---
layout: page
title: "AppDaemon API Reference"
description: "AppDaemon API Reference"
release_date: 2016-11-27 08:00:00 -0500
sidebar: true
comments: false
sharing: true
footer: true
hide_github_edit: true
---

## {% linkable_title Anatomy of an App %}

Automations in AppDaemon are performed by creating a piece of code (essentially a Python Class) and then instantiating it as an Object one or more times by configuring it as an App in the configuration file. The App is given a chance to register itself for whatever events it wants to subscribe to, and AppDaemon will then make calls back into the Object's code when those events occur, allowing the App to respond to the event with some kind of action.

The first step is to create a unique file within the apps directory (as defined in the `[AppDaemon]` section of configuration file). This file is in fact a Python module, and is expected to contain one or more classes derived from the supplied `AppDaemon` class, imported from the supplied `homeassistant.appapi` module. The start of an app might look like this:

```python
import homeassistant.appapi as appapi

class MotionLights(appapi.AppDaemon):
```

When configured as an app in the config file (more on that later) the lifecycle of the App begins. It will be instantiated as an object by AppDaemon, and immediately, it will have a call made to it's `initialize()` function - this function must appear as part of every app:

```python
  def initialize(self):
```

The initialize function allows the app to register any callbacks it might need for responding to state changes, and also any setup activities. When the `initialize()` function returns, the App will be dormant until any of it's callbacks are activated.

There are several circumstances under which `initialize()` might be called:

- Initial start of AppDaemon
- Following a change to the Class code
- Following a change to the module parameters
- Following initial configuration of an app
- Following a change in the status of Daylight Savings Time
- Following a restart of Home Assistant

In every case, the App is responsible for recreating any state it might need as if it were the first time it was ever started. If `initialize()` is called, the app can safely assume that it is either being loaded for the first time, or that all callbacks and timers have been cancelled. In either case, the APP will need to recreate them. Depending upon the application it may be desirable for the App to establish state such as whether or not a particular light is on, within the `initialize()` function to ensure that everything is as expected or to make immediate remedial action (e.g. turn off a light that might have been left on by mistake when the app was restarted).

After the `initialize()` function is in place, the rest of the app consists of functions that are called by the various callback mechanisms, and any additional functions the user wants to add as part of the program logic. Apps are able to subscribe to 2 main classes of events:

- Scheduled Events
- State Change Events

These, along with their various subscription calls and helper functions, will be described in detail in later sections.

To wrap up this section, here is a complete functioning App (with comments):

```python
import homeassistant.appapi as appapi
import datetime

# Declare Class
class NightLight(appapi.AppDaemon):
  #initialize() function which will be called at startup and reload
  def initialize(self):
    # Create a time object for 7pm
    time = datetime.time(19, 00, 0)
    # Schedule a daily callback that will call run_daily() at 7pm every night
    self.run_daily(self.run_daily_callback, time)

   # Our callback function will be called by the scheduler every day at 7pm
  def run_daily_callback(self, kwargs):
    # Call to Home Assistant to turn the porch light on
    self.turn_on("light.porch")
```

To summarize - an App's lifecycle consists of being initialized, which allows it to set one or more state and/or schedule callbacks. When those callbacks are activated, the App will typically use one of the Service Calling calls to effect some change to the devices of the system and then wait for the next relevant state change. That's all there is to it!

## {% linkable_title About the API %}

The implementation of the API is located in the AppDaemon class that Apps are derived from. The code for the functions is therefore available to the App simply by invoking the name of the function from the object namespace using the `self` keyword, as in the above examples. `self.turn_on()` for example is just a method defined in the parent class and made available to the child. This design decision was made to simplify some of the implementation and hide passing of unnecessary variables during the API invocation.

## {% linkable_title Configuration of Apps %}
Apps are configured by specifying new sections in the configuration file. `[AppDaemon]` is a reserved section, for configuration of AppDaemon itself. The name of the section is the name the App is referred to within the system in log files etc. and must be unique.

To configure a new App you need a minimum of two directives:

- `module` - the name of the module (without the `.py`) that contains the class to be used for this App
- `class` - the name of the class as defined within the module for the APPs code

Although the section/App name must be unique, it is possible to re-use a class as many times as you want, and conversely to put as many classes in a module as you want. A sample definition for a new App might look as follows:

```ini
[newapp]
module = new
class = NewApp
```

When AppDaemon sees the following configuration it will expect to find a class called `NewApp` defined in a module called `new.py` in the apps subdirectory. Apps can be placed at the root of the Apps directory or within a subdirectory, an arbitrary depth down - wherever the App is, as long as it is in some subdirectory of the Apps dir, or in the Apps dir itself, AppDaemon will find it. There is no need to include information about the path, just the name of the file itself (without the `.py`) is sufficient. If names in the subdirectories overlap, AppDir will pick one of them but the exact choice it will make is undefined.

When starting the system for the first time or when reloading an App or Module, the system will log the fact in it's main log. It is often the case that there is a problem with the class, maybe a syntax error or some other problem. If that is the case, details will be output to the error log allowing the user to remedy the problem and reload.

## {% linkable_title Steps to writing an App %}

1. Create the code in a new or shared module by deriving a class from AppDaemon, add required callbacks and code
2. Add the App to the configuration file
3. There is no number 3

## {% linkable_title Reloading Modules and Classes %}

Reloading of modules is automatic. When the system spots a change in a module, it will automatically reload and recompile the module. It will also figure out which Apps were using that Module and restart them, causing all of their existing callbacks to be cleared, and their `initialize()` function to be called.

The same is true if changes are made to an App's configuration - changing the class, or arguments (see later) will cause that app to be reloaded in the same way. The system is also capable of detecting if a new app has been added, or if one has been removed, and it will act appropriately, starting the new app immediately and removing all callbacks for the removed app.

The suggested order for creating a new App is to add the module code first and work until it compiles cleanly, and only then add an entry in the configuration file to actually run it. A good workflow is to continuously monitor the error file (using `tail -f` on Linux for instance) to ensure that errors are seen and can be remedied.

## {% linkable_title Passing Arguments to Apps %}

There wouldn't be much point in being able to run multiple versions of an App if there wasn't some way to instruct them to do something different. For this reason it is possible to pass any required arguments to an App, which are then made available to the object at runtime. The arguments themselves can be called anything (apart from `module` or `class`) and are simply added into the section after the 2 mandatory directives like so:

```ini
[MyApp]
module = myapp
class = MyApp
param1 = spam
param2 = eggs
```

Within the Apps code, the 2 parameters (as well as the module and class) are available as a dictionary called `args`, and accessed as follows:

```python
param1 = self.args["param1"]
param2 = self.args["param2"]
```

A use case for this might be an App that detects motion and turns on a light. If you have 3 places you want to run this, rather than hardcoding this into 3 separate Apps, you need only code a single app and instantiate it 3 times with different arguments. It might look something like this:

```ini
[downstairs_motion_light]
module = motion_light
class = MotionLight
sensor = binary_sensor.downstairs_hall
light = light.downstairs_hall
[upstairs_motion_light]
module = motion_light
class = MotionLight
sensor = binary_sensor.upstairs_hall
light = light.upstairs_hall
[garage_motion_light]
module = motion_light
class = MotionLight
sensor = binary_sensor.garage
light = light.garage
```

## {% linkable_title Callback Constraints %}

Callback constraints are a feature of AppDaemon that removes the need for repetition of some common coding checks. Many Apps will wish to process their callbacks only when certain conditions are met, e.g. someone is home, and it's after sunset. These kinds of conditions crop up a lot, and use of callback constraints can significantly simplify the logic required within callbacks.

Put simply, callback constraints are one or more conditions on callback execution that can be applied to an individual App. An App's callbacks will only be executed if all of the constraints are met. If a constraint is absent it will not be checked for.

For example, the presence callback constraint can be added to an App by adding a parameter to it's configuration like this:

```ini
[some_app]
module = some_module
class = SomeClass
constrain_presence = noone
```

Now, although the `initialize()` function will be called for MyClass, and it will have a chance to register as many callbacks as it desires, none of the callbacks will execute, in this case, until everyone has left. This could be useful for an interior motion detector App for instance. There are several different types of constraints:

- input_boolean
- input_select
- presence
- time

An App can have as many or as few as are required. When more than one constraint is present, they must all evaluate to true to allow the callbacks to be called. Constraints becoming true are not an event in their own right, but if they are all true at a point in time, the next callback that would otherwise been blocked due to constraint failure will now be called. Similarly, if one of the constraints becomes false, the next callback that would otherwise have been called will be blocked.

They are described individually below.

### {% linkable_title input_boolean %}
By default, the input_boolean constraint prevents callbacks unless the specified input_boolean is set to "on". This is useful to allow certain Apps to be turned on and off from the user interface. For example:

```ini
[some_app]
module = some_module
class = SomeClass
constrain_input_boolean = input_boolean.enable_motion_detection
```

If you want to reverse the logic so the constraint is only called when the input_boolean is off, use the optional state parameter by appending ",off" to the argument, e.g.:

```ini
[some_app]
module = some_module
class = SomeClass
constrain_input_boolean = input_boolean.enable_motion_detection,off
```

### {% linkable_title input_select %}
The input_select constraint prevents callbacks unless the specified input_select is set to one or more of the nominated (comma separated) values. This is useful to allow certain Apps to be turned on and off according to some flag, e.g. a house mode flag.

```ini
# Single value
constrain_input_select = input_select.house_mode,Day
# or multiple values
constrain_input_select = input_select.house_mode,Day,Evening,Night
```

### {% linkable_title presence %}
The presence constraint will constrain based on presence of device trackers. It takes 3 possible values:
- `noone` - only allow callback execution when no one is home
- `anyone` - only allow callback execution when one or more person is home
- `everyone` - only allow callback execution when everyone is home

```ini
constrain_presence = anyone
# or
constrain_presence = someone
# or
constrain_presence = noone
```

### {% linkable_title time %}
The time constraint consists of 2 variables, `constrain_start_time` and `constrain_end_time`. Callbacks will only be executed if the current time is between the start and end times.
- If both are absent no time constraint will exist
- If only start is present, end will default to 1 second before midnight
- If only end is present, start will default to midnight

The times are specified in a string format with one of the following formats:
- HH:MM:SS - the time in Hours Minutes and Seconds, 24 hour format.
- `sunrise`|`sunset` [+|- HH:MM:SS]- time of the next sunrise or sunset with an optional positive or negative offset in Hours Minutes and seconds

The time based constraint system correctly interprets start and end times that span midnight.

```ini
# Run between 8am and 10pm
constrain_start_time = 08:00:00
constrain_end_time = 22:00:00
# Run between sunrise and sunset
constrain_start_time = sunrise
constrain_end_time = sunset
# Run between 45 minutes before sunset and 45 minutes after sunrise the next day
constrain_start_time = sunset - 00:45:00
constrain_end_time = sunrise + 00:45:00
```

### {% linkable_title days %}
The day constraint consists of as list of days for which the callbacks will fire, e.g.

```ini
constrain_days = mon,tue,wed
```

Callback constraints can also be applied to individual callbacks within Apps, see later for more details.

## {% linkable_title A Note on Threading %}

AppDaemon is multithreaded. This means that any time code within an App is executed, it is executed by one of many threads. This is generally not a particularly important consideration for this application; in general, the execution time of callbacks is expected to be far quicker than the frequency of events causing them. However, it should be noted for completeness, that it is certainly possible for different pieces of code within the App to be executed concurrently, so some care may be necessary if different callback for instance inspect and change shared variables. This is a fairly standard caveat with concurrent programming, and if you know enough to want to do this, then you should know enough to put appropriate safeguards in place. For the average user however this shouldn't be an issue. If there are sufficient use cases to warrant it, I will consider adding locking to the function invocations to make the entire infrastructure threadsafe, but I am not convinced that it is necessary.

An additional caveat of a threaded worker pool environment is that it is the expectation that none of the callbacks tie threads up for a significant amount of time. To do so would eventually lead to thread exhaustion, which would make the system run behind events. No events would be lost as they would be queued, but callbacks would be delayed which is a bad thing.

Given the above, NEVER use Python's `time.sleep()` if you want to perform an operation some time in the future, as this will tie up a thread for the period of the sleep. Instead use the scheduler's `run_in()` function which will allow you to delay without blocking any threads.

## {% linkable_title State Operations %}

### {% linkable_title A note on Home Assistant State %}

State within Home Assistant is stored as a collection of dictionaries, one for each entity. Each entity's dictionary will have some common fields and a number of entity type specific fields The state for an entity will always have the attributes:

- `last_updated`
- `last_changed`
- `state`

Any other attributes such as brightness for a lamp will only be present if the entity supports them, and will be stored in a sub-dictionary called `attributes`. When specifying these optional attributes in the `get_state()` call, no special distinction is required between the main attributes and the optional ones - `get_state()` will figure it out for you.

Also bear in mind that some attributes such as brightness for a light, will not be present when the light is off.

In most cases, the attribute `state` has the most important value in it, e.g. for a light or switch this will be `on` or `off`, for a sensor it will be the value of that sensor. Many of the AppDaemon API calls and callbacks will implicitly return the value of state unless told to do otherwise.

### {% linkable_title get_state() %}

#### {% linkable_title Synopsis %}

```python
get_state(entity = None, attribute = None)
```

`get_state()` is used to query the state of any component within Home Assistant. State updates are continuously tracked so this call runs locally and does not require AppDaemon to call back to Home Assistant and as such is very efficient.

#### {% linkable_title Returns %}

`get_state()` returns a `dictionary` or single value, the structure of which varies according to the parameters used.

#### {% linkable_title Parameters %}

All parameters are optional, and if `get_state()` is called with no parameters it will return the entire state of Home Assistant at that given time. This will consist of a dictionary with a key for each entity. Under that key will be the standard entity state information.

##### {% linkable_title entity %}

This is the name of an entity or device type. If just a device type is provided, e.g. `light` or `binary_sensor`, `get_state()` will return a dictionary of all devices of that type, indexed by the entity_id, containing all the state for each entity.

If a fully qualified `entity_id` is provided, `get_state()` will return the state attribute for that entity, e.g. `on` or `off` for a light.

##### {% linkable_title attribute %}

Name of an attribute within the entity state object. If this parameter is specified in addition to a fully qualified `entity_id`, a single value representing the attribute will be returned, or `None` if it is not present.

The value `all` for attribute has special significance and will return the entire state dictionary for the specified entity rather than an individual attribute value.

#### {% linkable_title Examples %}

```python
# Return state for the entire system
state = self.get_state()

# Return state for all switches in the system
state = self.get_state("switch")

# Return the state attribute for light.office_1
state = self.get_state("light.office_1")

# Return the brightness attribute for light.office_1
state = self.get_state("light.office_1", "brightness")

# Return the entire state for light.office_1
state = self.get_state("light.office_1", "all")
```

### {% linkable_title set_state() %}

`set_state()` will make a call back to Home Assistant and make changes to the internal state of Home Assistant. This is not something that you would usually want to do and the applications are limited however the call is included for completeness. Note that for instance, setting the state of a light to `on` won't actually switch the device on, it will merely change the state of the device in Home Assistant so that it no longer reflects reality. In most cases, the state will be corrected the next time Home Assistant polls the device or someone causes a state change manually. To effect actual changes of devices use one of the service call functions.

One possible use case for `set_state()` is for testing. If for instance you are writing an App to turn on a light when it gets dark according to a luminance sensor, you can use `set_state()` to temporarily change the light level reported by the sensor to test your program. However this is also possible using the developer tools.

At the time of writing, it appears that no checking is done as to whether or not the entity exists, so it is possible to add entirely new entries to Home Assistant's state with this call.

#### {% linkable_title Synopsis %}

```python
set_state(entity_id, **kwargs)
```

#### {% linkable_title Returns %}

`set_state()` returns a dictionary representing the state of the device after the call has completed.

#### {% linkable_title Parameters %}

##### {% linkable_title entity_id %}

Entity id for which the state is to be set, e.g. `light.office_1`.

##### {% linkable_title values %}

A list of keyword values to be changed or added to the entities state. e.g. `state = "off"`. Note that any optional attributes such as colors for bulbs etc, need to reside in a dictionary called `attributes`; see the example.

#### {% linkable_title Examples %}

```python
status = self.set_state("light.office_1", state = "on", attributes = {"color_name": "red"})
```

### {% linkable_title About Callbacks %}

A large proportion of home automation revolves around waiting for something to happen and then reacting to it; a light level drops, the sun rises, a door opens etc. Home Assistant keeps track of every state change that occurs within the system and streams that information to AppDaemon almost immediately.

An individual App however usually doesn't care about the majority of state changes going on in the system; Apps usually care about something very specific, like a specific sensor or light. Apps need a way to be notified when a state change happens that they care about, and be able to ignore the rest. They do this through registering callbacks. A callback allows the App to describe exactly what it is interested in, and tells AppDaemon to make a call into its code in a specific place to be able to react to it - this is a very familiar concept to anyone familiar with event-based programming.

There are 3 types of callbacks within AppDaemon:

- State Callbacks - react to a change in state
- Scheduler Callbacks - react to a specific time or interval
- Event Callbacks - react to specific Home Assistant and Appdaemon events.

All callbacks allow the user to specify additional parameters to be handed to the callback via the standard Python `**kwargs` mechanism for greater flexibility.

### {% linkable_title About Registering Callbacks %}

Each of the various types of callback have their own function or functions for registering the callback:

- `listen_state()` for state callbacks
- Various scheduler calls such as `run_once()` for scheduler callbacks
- `listen_event()` for event callbacks.

Each type of callback shares a number of common mechanisms that increase flexibility.

#### {% linkable_title Callback Level Constraints %}

When registering a callback, you can add constraints identical to the Application level constraints described earlier. The difference is that a constraint applied to an individual callback only affects that callback and no other. The constraints are applied by adding Python keyword-value style arguments after the positional arguments. The parameters themselves are named identically to the previously described constraints and have identical functionality. For instance, adding:

`constrain_presence="everyone"`

to a callback registration will ensure that the callback is only run if the callback conditions are met and in addition everyone is present although any other callbacks might run whenever their event fires if they have no constraints.

For example:

`self.listen_state(self.motion, "binary_sensor.drive", constrain_presence="everyone")`

#### {% linkable_title User Arguments %}

Any callback has the ability to allow the App creator to pass through arbitrary keyword arguments that will be presented to the callback when it is run. The arguments are added after the positional parameters just like the constraints. The only restriction is that they cannot be the same as any constraint name for obvious reasons. For example, to pass the parameter `arg1 = "home assistant"` through to a callback you would register a callback as follows:

`self.listen_state(self.motion, "binary_sensor.drive", arg1="home assistant")`

Then in the callback you could use it as follows:

```python
def motion(self, entity, attribute, old, new, **kwargs):
    self.log("Arg1 is {}".format(kwargs["arg1"]))
```

### {% linkable_title State Callbacks %}

AppDaemons's state callbacks allow an App to listen to a wide variety of events, from every state change in the system, right down to a change of a single attribute of a particular entity. Setting up a callback is done using a single API call `listen_state()` which takes various arguments to allow it to do all of the above. Apps can register as many or as few callbacks as they want.

### {% linkable_title About State Callback Functions %}

When calling back into the App, the App must provide a class function with a known signature for AppDaemon to call. The callback will provide various information to the function to enable the function to respond appropriately. For state callbacks, a class defined callback function should look like this:

```python
  def my_callback(self, entity, attribute, old, new, **kwargs):
    <do some useful work here>
```

You can call the function whatever you like - you will reference it in the `listen_state()` call, and you can create as many callback functions as you need.

The parameters have the following meanings:

#### {% linkable_title self %}

A standard Python object reference.

#### {% linkable_title entity %}

Name of the entity the callback was requested for or `None`.

#### {% linkable_title attribute %}

Name of the attribute the callback was requested for or `None`.

#### {% linkable_title old %}

The value of the state before the state change.

#### {% linkable_title new %}

The value of the state after the state change.

`old` and `new` will have varying types depending on the type of callback.

#### {% linkable_title \*\*kwargs %}

A dictionary containing any constraints and/or additional user specific keyword arguments supplied to the `listen_state()` call.

### {% linkable_title listen_state() %}

`listen_state()` allows the user to register a callback for a wide variety of state changes.

#### {% linkable_title Synopsis %}

```python
handle = listen_state(callback, entity = None, **kwargs)
```

#### {% linkable_title Returns %}

A unique identifier that can be used to cancel the callback if required. Since variables created within object methods are local to the function they are created in, and in all likelihood the cancellation will be invoked later in a different function, it is recommended that handles are stored in the object namespace, e.g. `self.handle`.

#### {% linkable_title Parameters %}

All parameters except `callback` are optional, and if `listen_state()` is called with no additional parameters it will subscribe to any state change within Home Assistant.

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard State Callback format documented above.

##### {% linkable_title entity %}

This is the name of an entity or device type. If just a device type is provided, e.g. `light` or `binary_sensor`, `listen_state()` will subscribe to state changes of all devices of that type. If a fully qualified `entity_id` is provided, `listen_state()` will listen for state changes for just that entity.

When called, AppDaemon will supply the callback function, in old and new, with the state attribute for that entity, e.g. `on` or `off` for a light.

##### {% linkable_title attribute (optional) %}

Name of an attribute within the entity state object. If this parameter is specified in addition to a fully qualified `entity_id`, `listen_state()` will subscribe to changes for just that attribute within that specific entity. The new and old parameters in the callback function will be provided with a single value representing the attribute.

The value `all` for attribute has special significance and will listen for any state change within the specified entity, and supply the callback functions with the entire state dictionary for the specified entity rather than an individual attribute value.

##### {% linkable_title new = <value> (optional) %}

If `new` is supplied as a parameter, callbacks will only be made if the state of the selected attribute (usually `state`) in the new state match the value of `new`.

##### {% linkable_title old =  <value> (optional) %}

If `old` is supplied as a parameter, callbacks will only be made if the state of the selected attribute (usually `state`) in the old state match the value of `old`.

Note: `old` and `new` can be used singly or together.

##### {% linkable_title duration =  <seconds> (optional) %}

If duration is supplied as a parameter, the callback will not fire unless the state listened for is maintained for that number of seconds. This makes the most sense if a specific attribute is specified (or the default os `state` is used), an in conjunction with the `old` or `new` parameters, or both. When the callback is called, it is supplied with the values of `entity`, `attr`, `old` and `new` that were current at the time the actual event occured, since the assumption is that none of them have changed in the intervening period.

```python
  def my_callback(self, **kwargs):
    <do some useful work here>
```

(Scheduler callbacks are documented in detail laer in this document)

##### {% linkable_title \*\*kwargs %}

Zero or more keyword arguments that will be supplied to the callback when it is called.

#### {% linkable_title Examples %}

```python
# Listen for any state change and return the state attribute
self.handle = self.listen_state(self.my_callback)

# Listen for any state change involving a light and return the state attribute
self.handle = self.listen_state(self.my_callback, "light")

# Listen for a state change involving light.office1 and return the state attribute
self.handle = self.listen_state(self.my_callback, "light.office_1")

# Listen for a state change involving light.office1 and return the entire state as a dict
self.handle = self.listen_state(self.my_callback, "light.office_1", attribute = "all")

# Listen for a state change involving the brightness attribute of light.office1
self.handle = self.listen_state(self.my_callback, "light.office_1", attribute = "brightness")

# Listen for a state change involving light.office1 turning on and return the state attribute
self.handle = self.listen_state(self.my_callback, "light.office_1", new = "on")

# Listen for a state change involving light.office1 changing from brightness 100 to 200 and return the state attribute
self.handle = self.listen_state(self.my_callback, "light.office_1", old = "100", new = "200")

# Listen for a state change involving light.office1 changing to state on and remaining on for a minute
self.handle = self.listen_state(self.my_callback, "light.office_1", new = "on", duration = 60)

```

### {% linkable_title cancel_listen_state() %}

Cancel a `listen_state()` callback. This will mean that the App will no longer be notified for the specific state change that has been cancelled. Other state changes will continue to be monitored.

#### {% linkable_title Synopsis %}

```python
cancel_listen_state(handle)
```

#### {% linkable_title Returns %}

Nothing

#### {% linkable_title Parameters %}

##### {% linkable_title handle %}

The handle returned when the `listen_state()` call was made.

#### {% linkable_title Examples %}

```python
self.cancel_listen_state(self.office_light_handle)
```

### {% linkable_title info_listen_state() %}

Get information on state a callback from it's handle.

#### {% linkable_title Synopsis %}

```python
entity, attribute, kwargs = self.info_listen_state(self.handle)
```

#### {% linkable_title Returns %}

entity, attribute, kwargs - the values supplied when the callback was initially created.

#### {% linkable_title Parameters %}

##### {% linkable_title handle %}

The handle returned when the `listen_state()` call was made.

#### {% linkable_title Examples %}

```python
entity, attribute, kwargs = self.info_listen_state(self.handle)
```

## {% linkable_title Scheduler %}

AppDaemon contains a powerful scheduler that is able to run with 1 second resolution to fire off specific events at set times, or after set delays, or even relative to sunrise and sunset. In general, events should be fired less than a second after specified but under certain circumstances there may be short additional delays.

### {% linkable_title About Schedule Callbacks %}

As with State Change callbacks, Scheduler Callbacks expect to call into functions with a known and specific signature and a class defined Scheduler callback function should look like this:

```python
  def my_callback(self, **kwargs):
    <do some useful work here>
```

You can call the function whatever you like; you will reference it in the Scheduler call, and you can create as many callback functions as you need.

The parameters have the following meanings:

#### {% linkable_title self %}
A standard Python object reference

#### {% linkable_title \*\*kwargs %}

A dictionary containing Zero or more keyword arguments to be supplied to the callback.

### {% linkable_title Creation of Scheduler Callbacks %}

Scheduler callbacks are created through use of a number of convenience functions which can be used to suit the situation.

#### {% linkable_title run_in() %}

Run the callback in a defined number of seconds. This is used to add a delay, for instance a 60 second delay before a light is turned off after it has been triggered by a motion detector. This callback should always be used instead of `time.sleep()` as discussed previously.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_in(callback, delay, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer.

#### {% linkable_title Parameters %}

##### vcallback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title delay %}

Delay, in seconds before the callback is invoked.

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
self.handle = self.run_in(self.run_in_c)
self.handle = self.run_in(self.run_in_c, title = "run_in5")
```
#### {% linkable_title run_once() %}

Run the callback once, at the specified time of day. If the time of day is in the past, the callback will occur on the next day.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_once(callback, time, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer.

#### {% linkable_title Parameters %}

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title time %}

A Python `time` object that specifies when the callback will occur. If the time specified is in the past, the callback will occur the next day at the specified time.

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
# Run at 4pm today, or 4pm tomorrow if it is already after 4pm
import datetime
...
runtime = datetime.time(16, 0, 0)
handle = self.run_once(self.run_once_c, runtime)
```

#### {% linkable_title run_at() %}

Run the callback once, at the specified date and time.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_at(callback, datetime, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer. `run_at()` will raise an exception if the specified time is in the past.

#### {% linkable_title Parameters %}

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title datetime %}

A Python `datetime` object that specifies when the callback will occur.

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
# Run at 4pm today
import datetime
...
runtime = datetime.time(16, 0, 0)
today = datetime.date.today()
event = datetime.datetime.combine(today, runtime)
handle = self.run_once(self.run_once_c, event)
```
#### {% linkable_title run_daily() %}

Execute a callback at the same time every day. If the time has already passed, the function will not be invoked until the following day at the specified time.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_daily(callback, time, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer.

#### {% linkable_title Parameters %}

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title time %}

A Python `time` object that specifies when the callback will occur. If the time specified is in the past, the callback will occur the next day at the specified time.

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
# Run daily at 7pm
import datetime
...
time = datetime.time(19, 0, 0)
self.run_daily(self.run_daily_c, runtime)
```

#### {% linkable_title run_hourly() %}

Execute a callback at the same time every hour. If the time has already passed, the function will not be invoked until the following hour at the specified time.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_hourly(callback, time = None, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer.

#### {% linkable_title Parameters %}

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title time %}

A Python `time` object that specifies when the callback will occur, the hour component of the time object is ignored. If the time specified is in the past, the callback will occur the next hour at the specified time. If time is not supplied, the callback will start an hour from the time that `run_hourly()` was executed.

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
# Run every hour, on the hour
import datetime
...
time = datetime.time(0, 0, 0)
self.run_daily(self.run_daily_c, runtime)
```
#### {% linkable_title run_minutely() %}

Execute a callback at the same time every minute. If the time has already passed, the function will not be invoked until the following minute at the specified time.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_minutely(callback, time = None, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer.

#### {% linkable_title Parameters %}

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title time %}

A Python `time` object that specifies when the callback will occur, the hour and minute components of the time object are ignored. If the time specified is in the past, the callback will occur the next hour at the specified time. If time is not supplied, the callback will start a minute from the time that `run_minutely()` was executed.

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
# Run Every Minute on the minute
import datetime
...
time = datetime.time(0, 0, 0)
self.run_minutely(self.run_minutely_c, time)
```

#### {% linkable_title run_every() %}

Execute a repeating callback with a configurable delay starting at a specific time.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_every(callback, time, repeat, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer.

#### {% linkable_title Parameters %}

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title time %}

A Python `time` object that specifies when the initial callback will occur.

##### {% linkable_title repeat %}

After the initial callback has occurred, another will occur every `repeat` seconds.

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
# Run every 17 minutes starting in 2 hours time
import datetime
...
self.run_every(self.run_every_c, time, 17 * 60)
```

#### {% linkable_title cancel_timer() %}
Cancel a previously created timer

#### {% linkable_title Synopsis %}

```python
self.cancel_timer(handle)
```

#### {% linkable_title Returns %}

None

#### {% linkable_title Parameters %}

##### {% linkable_title handle %}

A handle value returned from the original call to create the timer.

#### {% linkable_title Examples %}

```python
self.cancel_timer(handle)
```

### {% linkable_title info_timer() %}

Get information on a scheduler event from it's handle.

#### {% linkable_title Synopsis %}

```python
time, interval, kwargs = self.info_timer(handle)
```

#### {% linkable_title Returns %}

time - datetime object representing the next time the callback will be fired

interval - repeat interval if applicable, `0` otherwise.

kwargs - the values supplied when the callback was initially created.

#### {% linkable_title Parameters %}

##### {% linkable_title handle %}

The handle returned when the scheduler call was made.

#### {% linkable_title Examples %}

```python
time, interval, kwargs = self.info_timer(handle)
```

### {% linkable_title Scheduler Ransomization %}

All of the scheduler calls above support 2 additional optional arguments, `random_start` and `random_end`. Using these arguments it is possible to randomize the firing of callbacks to the degree desired by setting the appropriate number of seconds with the parameters.

- `random_start` - start of range of the random time
- `random_end` - end of range of the random time 

`random_start` must always be numerically lower than `random_end`, they can be negative to denote a random offset before and event, or positive to denote a random offset after an event. The event would be a an absolute or relative time or sunrise/sunset depending on whcih scheduler call you use and these values affect the base time by the spcified amount. If not specified, they will default to `0`.

For example:

```python
# Run a callback in 2 minutes minus a random number of seconds between 0 and 60, e.g. run between 60 and 120 seconds from now
self.handle = self.run_in(callback, 120, random_start = -60, **kwargs)
# Run a callback in 2 minutes plus a random number of seconds between 0 and 60, e.g. run between 120 and 180 seconds from now
self.handle = self.run_in(callback, 120, random_end = 60, **kwargs)
# Run a callback in 2 minutes plus or minus a random number of seconds between 0 and 60, e.g. run between 60 and 180 seconds from now
self.handle = self.run_in(callback, 120, random_start = -60, random_end = 60, **kwargs)
```

## {% linkable_title Sunrise and Sunset %}

AppDaemon has a number of features to allow easy tracking of sunrise and sunset as well as a couple of scheduler functions. Note that the scheduler functions also support the randomization parameters described above, but they cannot be used in conjunction with the `offset` parameter`.

### {% linkable_title run_at_sunrise() %}

Run a callback at or around sunrise.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_at_sunrise(callback, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer.

#### {% linkable_title Parameters %}

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title offset = <seconds> %}

The time in seconds that the callback should be delayed after sunrise. A negative value will result in the callback occurring before sunrise. This parameter cannot be combined with `random_start` or `random_end`

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
import datetime
...
# Run 45 minutes before sunset
self.run_at_sunrise(self.sun, offset = datetime.timedelta(minutes = -45).total_seconds(), "Sunrise -45 mins")
# or you can just do the math yourself
self.run_at_sunrise(self.sun, offset = 30 * 60, "Sunrise +30 mins")
# Run at a random time +/- 60 minutes from sunrise
self.run_at_sunrise(self.sun, random_start = -60*60, random_end = 60*60, "Sunrise, random +/- 60 mins")
# Run at a random time between 30 and 60 minutes before sunrise
self.run_at_sunrise(self.sun, random_start = -60*60, random_end = 30*60, "Sunrise, random - 30 - 60 mins")
```

### {% linkable_title run_at_sunset() %}

Run a callback at or around sunset.

#### {% linkable_title Synopsis %}

```python
self.handle = self.run_at_sunset(callback, offset, **kwargs)
```

#### {% linkable_title Returns %}

A handle that can be used to cancel the timer.

#### {% linkable_title Parameters %}

##### {% linkable_title callback %}

Function to be invoked when the requested state change occurs. It must conform to the standard Scheduler Callback format documented above.

##### {% linkable_title offset = <seconds> %}

The time in seconds that the callback should be delayed after sunrise. A negative value will result in the callback occurring before sunrise. This parameter cannot be combined with `random_start` or `random_end`

##### {% linkable_title \*\*kwargs %}

Arbitary keyword parameters to be provided to the callback function when it is invoked.

#### {% linkable_title Examples %}

```python
# Example using timedelta
import datetime
...
self.run_at_sunset(self.sun, datetime.timedelta(minutes = -45).total_seconds(), "Sunset -45 mins")
# or you can just do the math yourself
self.run_at_sunset(self.sun, 30 * 60, "Sunset +30 mins")
# Run at a random time +/- 60 minutes from sunset
self.run_at_sunset(self.sun, random_start = -60*60, random_end = 60*60, "Sunset, random +/- 60 mins")
# Run at a random time between 30 and 60 minutes before sunset
self.run_at_sunset(self.sun, random_start = -60*60, random_end = 30*60, "Sunset, random - 30 - 60 mins")
```
### {% linkable_title sunrise() %}

Return the time that the next Sunrise will occur.

#### {% linkable_title Synopsis %}

```python
self.sunrise()
```

#### {% linkable_title Returns %}

A Python datetime that represents the next time Sunrise will occur.

#### {% linkable_title Examples %}

```python
rise_time = self.sunrise()
```
### {% linkable_title sunset() %}

Return the time that the next Sunset will occur.

#### {% linkable_title Synopsis %}

```python
self.sunset()
```

#### {% linkable_title Returns %}

A Python datetime that represents the next time Sunset will occur.

#### {% linkable_title Examples %}

```python
set_time = self.sunset()
```
### {% linkable_title sun_up() %}

A function that allows you to determine if the sun is currently up.

#### {% linkable_title Synopsis %}

```python
result = self.sun_up()
```

#### {% linkable_title Returns %}

`True` if the sun is up, False otherwise.

#### {% linkable_title Examples %}

```python
if self.sun_up():
    do something
```

### {% linkable_title sun_down() %}

A function that allows you to determine if the sun is currently down.

#### {% linkable_title Synopsis %}

```python
result = self.sun_down()
```

#### {% linkable_title Returns %}

`True` if the sun is down, False otherwise.

#### {% linkable_title Examples %}

```python
if self.sun_down():
    do something
```

## {% linkable_title Calling Services %}

### {% linkable_title About Services %}

Services within Home Assistant are how changes are made to the system and its devices. Services can be used to turn lights on and off, set thermostats and a whole number of other things. Home Assistant supplies a single interface to all these disparate services that take arbitrary parameters. AppDaemon provides the `call_service()` function to call into Home Assistant and run a service. In addition, it also provides convenience functions for some of the more common services making calling them a little easier.

### {% linkable_title call_service() %}

Call service is the basic way of calling a service within AppDaemon. It can call any service and provide any required parameters. Available services can be found using the developer tools in the UI. For listed services, the part before the first period is the domain, and the part after is the service name. For instance, `light.turn_on` has a domain of `light` and a service name of `turn_on`.

#### {% linkable_title Synopsis %}

```python
self.call_service(self, service, **kwargs)
```

#### {% linkable_title Returns %}

None

#### {% linkable_title Parameters %}

##### {% linkable_title service %}

The service name, e.g. `light.turn_on`.

##### {% linkable_title \*\*kwargs %}

Each service has different parameter requirements. This argument allows you to specify a comma separated list of keyword value pairs, e.g. `entity_id = light.office_1`. These parameters will be different for every service and can be discovered using the developer tools. Most if not all service calls require an `entity_id` however, so use of the above example is very common with this call.

#### {% linkable_title Examples %}

```python
self.call_service("light/turn_on", entity_id = "light.office_lamp", color_name = "red")
self.call_service("notify/notify", title = "Hello", message = "Hello World")
```
### {% linkable_title turn_on() %}

This is a convenience function for the `homassistant.turn_on` function. It is able to turn on pretty much anything in Home Assistant that can be turned on or run:

- Lights
- Switches
- Scenes
- Scripts

And many more.

#### {% linkable_title Synopsis %}

```python
self.turn_on(entity_id, **kwargs)
```

#### {% linkable_title Returns %}

None

#### {% linkable_title Parameters %}

##### {% linkable_title entity_id %}

Fully qualified entity_id of the thing to be turned on, e.g. `light.office_lamp` or ```scene.downstairs_on```

##### {% linkable_title \*\*kwargs %}

A comma separated list of key value pairs to allow specification of parameters over and above `entity_id`.

#### {% linkable_title Examples %}

```python
self.turn_on("switch.patio_lights")
self.turn_on("scene.bedrrom_on")
self.turn_on("light.office_1", color_name = "green")
```

### {% linkable_title turn_off() %}

This is a convenience function for the `homassistant.turn_off` function. Like `homeassistant.turn_on`, it is able to turn off pretty much anything in Home Assistant that can be turned off.

#### {% linkable_title Synopsis %}

```python
self.turn_off(entity_id)
```

#### {% linkable_title Returns %}

None

#### {% linkable_title Parameters %}

##### {% linkable_title entity_id %}

Fully qualified entity_id of the thing to be turned off, e.g. `light.office_lamp` or `scene.downstairs_on`.

#### {% linkable_title Examples %}

```python
self.turn_off("switch.patio_lights")
self.turn_off("light.office_1")
```

### {% linkable_title toggle() %}

This is a convenience function for the `homassistant.toggle` function. It is able to flip the state of pretty much anything in Home Assistant that can be turned on or off.

#### {% linkable_title Synopsis %}

```python
self.toggle(entity_id)
```

#### {% linkable_title Returns %}

None

#### {% linkable_title Parameters %}

##### {% linkable_title entity_id %}

Fully qualified entity_id of the thing to be toggled, e.g. `light.office_lamp` or `scene.downstairs_on`.

#### {% linkable_title Examples %}

```python
self.toggle("switch.patio_lights")
self.toggle("light.office_1", color_name = "green")
```

### {% linkable_title select_value() %}

This is a convenience function for the `input_slider.select_value` function. It is able to set the value of an input_slider in Home Assistant.

#### {% linkable_title Synopsis %}

```python
self.select_value(entity_id, value)
```

#### {% linkable_title Returns %}

None

#### {% linkable_title Parameters %}

##### {% linkable_title entity_id %}

Fully qualified entity_id of the input_slider to be changed, e.g. `input_slider.alarm_hour`.

##### {% linkable_title value %}

The new value to set the input slider to.

#### {% linkable_title Examples %}

```python
self.select_value("input_slider.alarm_hour", 6)
```

### {% linkable_title select_option() %}

This is a convenience function for the `input_select.select_option` function. It is able to set the value of an input_select in Home Assistant.

#### {% linkable_title Synopsis %}

```python
self.select_option(entity_id, option)
```

#### {% linkable_title Returns %}

None

#### {% linkable_title Parameters %}

##### {% linkable_title entity_id %}

Fully qualified entity_id of the input_select to be changed, e.g. `input_select.mode`.

##### {% linkable_title value %}

The new value to set the input slider to.

#### {% linkable_title Examples %}

```python
self.select_option("input_select.mode", "Day")
```

### {% linkable_title notify() %}

This is a convenience function for the `notify.notify` service. It will send a notification to your defualt notification service. If you have more than one, use `call_service()` to call the specific notification service you require instead.

#### {% linkable_title Synopsis %}

```python
notify(message, title=None)
```
#### {% linkable_title Returns %}

None

#### {% linkable_title Parameters %}

##### {% linkable_title message %}

Message to be sent to the notification service.

##### {% linkable_title title %}

Title of the notification - optional.

#### {% linkable_title Examples %}

```python
self.notify("", "Switching mode to Evening")
```

## {% linkable_title Events %}

### {% linkable_title About Events %}

Events are a fundamental part of how Home Assistant works under the covers. HA has an event bus that all components can read and write to, enabling components to inform other components when important events take place. We have already seen how state changes can be propagated to AppDaemon - a state change however is merely an example of an event within Home Assistant. There are several other event types, among them are:

- `homeassistant_start`
- `homeassistant_stop`
- `state_changed`
- `service_registered`
- `call_service`
- `service_executed`
- `platform_discovered`
- `component_loaded`

Using AppDaemon, it is possible to subscribe to specific events as well as fire off events.

In addition to the Home Assistant supplied events, AppDaemon adds 2 more events. These are internal to AppDaemon and are not visible on the Home Assistant bus:

- `appd_started` - fired once when AppDaemon is first started and after Apps are initialized
- `ha_started` - fired every time AppDaemon detects a Home Assistant restart

### {% linkable_title About Event Callbacks %}

As with State Change and Scheduler callbacks, Event Callbacks expect to call into functions with a known and specific signature and a class defined Scheduler callback function should look like this:

```python
  def my_callback(self, event_name, data, kwargs):
    <do some useful work here>
```

You can call the function whatever you like - you will reference it in the Scheduler call, and you can create as many callback functions as you need.

The parameters have the following meanings:

#### {% linkable_title self %}

A standard Python object reference.

#### {% linkable_title event_name %}

Name of the event that was called, e.g. `call_service`.

#### {% linkable_title data %}

Any data that the system supplied with the event as a dict.

#### {% linkable_title kwargs %}

A dictionary containing Zero or more user keyword arguments to be supplied to the callback.

### {% linkable_title listen_event() %}

Listen event sets up a callback for a specific event, or any event.

#### {% linkable_title Synopsis %}

```python
handle = listen_event(function, event = None, **kwargs):
```
#### {% linkable_title Returns %}

A handle that can be used to cancel the callback.

#### {% linkable_title Parameters %}

##### {% linkable_title function %}

The function to be called when the event is fired.

##### {% linkable_title event %}

Name of the event to subscribe to. Can be a standard Home Assistant event such as `service_registered` or an arbitrary custom event such as `"MODE_CHANGE"`. If no event is specified, `listen_event()` will subscribe to all events.

##### {% linkable_title \*\*kwargs (optional) %}

One or more keyword value pairs representing App specific parameters to supply to the callback. If the keywords match values within the event data, they will act as filters, meaning that if they don't match the values, the callback will not fire.

As an example of this, a Minimote controller when activated will generate an event called `zwave.scene_activated`, along with 2 pieces of data that are specific to the event - `entity_id` and `scene`. If you include keyword values for either of those, the values supplied to the `listen_event()1 call must match the values in the event or it will not fire. If the keywords do not match any of the data in the event they are simply ignored.

Filtering will work with any event type, but it will be necessary to figure out the data associated with the event to understand what values can be filtered on. This can be achieved by examining Home Assistant's logfiles when the event fires.

#### {% linkable_title Examples %}

```python
self.listen_event(self.mode_event, "MODE_CHANGE")
# Listen for a minimote event activating scene 3:
self.listen_event(self.generic_event, "zwave.scene_activated", scene_id = 3)
# Listen for a minimote event activating scene 3 from a specific minimote:
self.listen_event(self.generic_event, "zwave.scene_activated", entity_id = "minimote_31", scene_id = 3)
```

### {% linkable_title cancel_listen_event() %}

Cancels callbacks for a specific event.

#### {% linkable_title Synopsis %}

```python
cancel_listen_event(handle)
```
#### {% linkable_title Returns %}

None.

#### {% linkable_title Parameters %}

##### handle

A handle returned from a previous call to `listen_event()`.

#### {% linkable_title Examples %}

```python
self.cancel_listen_event(handle)
```

### {% linkable_title info_listen_event() %}

Get information on an event callback from it's handle.

#### {% linkable_title Synopsis %}

```python
service, kwargs = self.info_listen_event(handle)
```

#### {% linkable_title Returns %}

service, kwargs - the values supplied when the callback was initially created.

#### {% linkable_title Parameters %}

##### {% linkable_title handle %}

The handle returned when the `listen_event()` call was made.

#### {% linkable_title Examples %}

```python
service, kwargs = self.info_listen_event(handle)
```


### {% linkable_title fire_event() %}

Fire an event on the HomeAssistant bus, for other components to hear.

#### {% linkable_title Synopsis %}

```python
fire_event(event, **kwargs)
```

#### {% linkable_title Returns %}

None.

#### {% linkable_title Parameters %}

##### {% linkable_title event %}

Name of the event. Can be a standard Home Assistant event such as `service_registered` or an arbitrary custom event such as `"MODE_CHANGE"`.

##### {% linkable_title \*\*kwargs %}

Zero or more keyword arguments that will be supplied as part of the event.

#### {% linkable_title Examples %}

```python
self.fire_event("MY_CUSTOM_EVENT", jam="true")
```

### {% linkable_title Event Callback Function Signature %}

Functions called as an event callback will be supplied with 2 arguments:

```python
def service(self, event_name, data):
```

#### {% linkable_title event_name %}

The name of the event that caused the callback, e.g. `"MODE_CHANGE"` or `call_service`.

#### {% linkable_title data %}

A dictionary containing any additional information associated with the event.

### {% linkable_title Use of Events for Signalling between Home Assistant and AppDaemon %}

Home Assistant allows for the creation of custom events and existing components can send and receive them. This provides a useful mechanism for signaling back and forth between Home Assistant and AppDaemon. For instance, if you would like to create a UI Element to fire off some code in Home Assistant, all that is necessary is to create a script to fire a custom event, then subscribe to that event in AppDaemon. The script would look something like this:

```yaml
alias: Day
sequence:
- event: MODE_CHANGE
  event_data:
    mode: Day
```

The custom event `MODE_CHANGE` would be subscribed to with:

```python
self.listen_event(self.mode_event, "MODE_CHANGE")
```

Home Assistant can send these events in a variety of other places - within automations, and also directly from Alexa intents. Home Assistant can also listen for custom events with it's automation component. This can be used to signal from AppDaemon code back to home assistant. Here is a sample automation:

```yaml
automation:
  trigger:
    platform: event
    event_type: MODE_CHANGE
    ...
    ...
```

This can be triggered with a call to AppDaemon's fire_event() as follows:

```python
self.fire_event("MODE_CHANGE", mode = "Day")
```

## {% linkable_title Presence %}

Presence in Home Assistant is tracked using Device Trackers. The state of all device trackers can be found using the `get_state()` call, however AppDaemon provides several convenience functions to make this easier.

### {% linkable_title get_trackers() %}

Return a list of all device trackers. This is designed to be iterated over.

#### {% linkable_title Synopsis %}

```python
tracker_list = get_trackers()
```
#### {% linkable_title Returns %}

An iterable list of all device trackers.

#### {% linkable_title Examples %}

```python
trackers = self.get_trackers()
for tracker in trackers:
    do something
```

### {% linkable_title get_tracker_state() %}

Get the state of a tracker. The values returned depend in part on the configuration and type of device trackers in the system. Simpler tracker types like `Locative` or `NMAP` will return one of 2 states:

- `home`
- `not_home`

Some types of device tracker are in addition able to supply locations that have been configured as Geofences, in which case the name of that location can be returned.

#### {% linkable_title Synopsis %}

```python
location = self.get_tracker_state(tracker_id)
```

#### {% linkable_title Returns %}

A string representing the location of the tracker.

#### {% linkable_title Parameters %}

##### {% linkable_title tracker_id %}

Fully qualified entity_id of the device tracker to query, e.g. `device_tracker.andrew`.

#### {% linkable_title Examples %}

```python
trackers = self.get_trackers()
for tracker in trackers:
  self.log("{} is {}".format(tracker, self.get_tracker_state(tracker)))
```

### {% linkable_title everyone_home() %}

A convenience function to determine if everyone is home. Use this in preference to getting the state of `group.all_devices()` as it avoids a race condition when using state change callbacks for device trackers.

#### {% linkable_title Synopsis %}

```python
result = self.everyone_home()
```
#### {% linkable_title Returns %}

Returns `True` if everyone is at home, `False` otherwise.

#### {% linkable_title Examples %}

```python
if self.everyone_home():
    do something
```
### {% linkable_title anyone_home() %}

A convenience function to determine if one or more person is home. Use this in preference to getting the state of `group.all_devices()` as it avoids a race condition when using state change callbacks for device trackers.

#### {% linkable_title Synopsis %}

```python
result = self.anyone_home()
```

#### {% linkable_title Returns %}

Returns `True` if anyone is at home, `False` otherwise.

#### {% linkable_title Examples %}

```python
if self.anyone_home():
    do something
```
### {% linkable_title noone_home() %}

A convenience function to determine if no people are at home. Use this in preference to getting the state of group.all_devices() as it avoids a race condition when using state change callbacks for device trackers.

#### {% linkable_title Synopsis %}

```python
result = self.noone_home()
```

#### {% linkable_title Returns %}

Returns `True` if no one is home, `False` otherwise.

#### {% linkable_title Examples %}

```python
if self.noone_home():
    do something
```

## {% linkable_title Miscellaneous Helper Functions %}

### {% linkable_title time() %}

Returns a python `time` object representing the current time. Use this in preference to the standard Python ways to discover the current time, especially when using the "Time Travel" feature for testing.

#### {% linkable_title Synopsis %}

```python
time()
```

#### {% linkable_title Returns %}

A localised Python time object representing the current AppDaemon time.

#### {% linkable_title Parameters %}

None

#### {% linkable_title Example %}

```python
now = self.time()
```

### {% linkable_title date() %}

Returns a python `date` object representing the current date. Use this in preference to the standard Python ways to discover the current date, especially when using the "Time Travel" feature for testing.

#### {% linkable_title Synopsis %}

```python
date()
```

#### {% linkable_title Returns %}

A localised Python time object representing the current AppDaemon date.

#### {% linkable_title Parameters %}

None

#### {% linkable_title Example %}

```python
today = self.date()
```

### {% linkable_title datetime() %}

Returns a python `datetime` object representing the current date and time. Use this in preference to the standard Python ways to discover the current time, especially when using the "Time Travel" feature for testing.

#### {% linkable_title Synopsis %}

```python
datetime()
```

#### {% linkable_title Returns %}

A localised Python datetime object representing the current AppDaemon date and time.

#### {% linkable_title Parameters %}

None

#### {% linkable_title Example %}

```python
now = self.datetime()
```


### {% linkable_title convert_utc() %}

Home Assistant provides timestamps of several different sorts that may be used to gain additional insight into state changes. These timestamps are in UTC and are coded as ISO 8601 Combined date and time strings. `convert_utc()` will accept one of these strings and convert it to a localised Python datetime object representing the timestamp

#### {% linkable_title Synopsis %}

```python
convert_utc(utc_string)
```

#### {% linkable_title Returns %}

`convert_utc(utc_string)` returns a localised Python datetime object representing the timestamp.

#### {% linkable_title Parameters %}

##### {% linkable_title utc_string %}

An ISO 8601 encoded date and time string in the following format: `2016-07-13T14:24:02.040658-04:00`

#### {% linkable_title Example %}

###{% linkable_title parse_time() %}

Takes a string representation of a time, or sunrise or sunset offset and converts it to a `datetime.time` object.

#### {% linkable_title Synopsis %}

```python
parse_time(time_string)
```

#### {% linkable_title Returns %}

A `datetime.time` object, representing the time given in the `time_string` argument.

#### {% linkable_title Parameters %}

##### {% linkable_title time_string %}

A representation of the time in a string format with one of the following formats:

- HH:MM:SS - the time in Hours Minutes and Seconds, 24 hour format.
- sunrise &#124; sunset [+ &#124; - HH:MM:SS]- time of the next sunrise or sunset with an optional positive or negative offset in Hours Minutes and seconds

#### {% linkable_title Example %}

```python
time = self.parse_time("17:30:00")
time = self.parse_time("sunrise")
time = self.parse_time("sunset + 00:30:00")
time = self.parse_time("sunrise + 01:00:00")
```

### {% linkable_title now_is_between() %}

Takes two string representations of a time, or sunrise or sunset offset and returns true if the current time is between those 2 times. `now_is_between()` can correctly handle transitions across midnight.

#### {% linkable_title Synopsis %}

```python
now_is_between(start_time_string, end_time_string)
```

#### {% linkable_title Returns %}

`True` if the current time is within the specified start and end times, `False` otherwise.

#### {% linkable_title Parameters %}

##### {% linkable_title start_time_string, end_time_string %}

A representation of the start and end time respectively in a string format with one of the following formats:

- HH:MM:SS - the time in Hours Minutes and Seconds, 24 hour format.
- sunrise &#124; sunset [+ &#124; - HH:MM:SS]- time of the next sunrise or sunset with an optional positive or negative offset in Hours Minutes and seconds

#### {% linkable_title Example %}

```python
if self.now_is_between("17:30:00", "08:00:00"):
    do something
if self.now_is_between("sunset - 00:45:00", "sunrise + 00:45:00"):
    do something
```

### {% linkable_title friendly_name() %}

`frindly_name()` will return the Friendly Name of an entity if it has one.

#### {% linkable_title Synopsis %}

```python
Name = self.friendly_name(entity_id)
```

#### {% linkable_title Returns %}

The friendly name of the entity if it exists or the entity id if not.

#### {% linkable_title Example %}

```python
tracker = "device_tracker.andrew"
self.log("{}  ({}) is {}".format(tracker, self.friendly_name(tracker), self.get_tracker_state(tracker)))
```

### {% linkable_title split_entity() %}

`split_entity()` will take a fully qualified entity id of the form `light.hall_light` and split it into 2 values, the device and the entity, e.g. `light` and `hall_light`.

#### {% linkable_title Synopsis %}

```python
device, entity = self.split_entity(entity_id)
```

#### {% linkable_title Parameters %}

##### {% linkable_title entity_id %}

Fully qualified entity id to be split.

#### {% linkable_title Returns %}

A list with 2 entries, the device and entity respectively.

#### {% linkable_title Example %}

```python
device, entity = self.split_entity(entity_id)
if device == "scene":
    do something specific to scenes
```


### {% linkable_title get_app() %}

`get_app()` will return the instantiated object of another app running within the system. This is useful for calling functions or accessing variables that reside in different apps without requiring duplication of code.

#### {% linkable_title Synopsis %}

```python
get_app(self, name)
```
#### {% linkable_title Parameters %}

##### {% linkable_title name %}

Name of the app required. This is the name specified in header section of the config file, not the module or class.

#### {% linkable_title Returns %}

An object reference to the class.

#### {% linkable_title Example %}
```python
MyApp = self.get_app("MotionLights")
MyApp.turn_light_on()
```

### {% linkable_title split_device_list() %}

`split_device_list()` will take a comma separated list of device types (or anything else for that matter) and return them as an iterable list. This is intended to assist in use cases where the App takes a list of entities from an argument, e.g. a list of sensors to monitor. If only one entry is provided, an iterable list will still be returned to avoid the need for special processing.

#### {% linkable_title Synopsis %}

```python
devices = split_device_list(list)
```

#### {% linkable_title Returns %}

A list of split devices with 1 or more entries.

#### {% linkable_title Example %}

```python
for sensor in self.split_device_list(self.args["sensors"]):
    do something for each sensor, e.g. make a state subscription
```


### {% linkable_title Writing to Logfiles %}

AppDaemon uses 2 separate logs - the general log and the error log. An AppDaemon App can write to either of these using the supplied convenience methods `log()` and `error()`, which are provided as part of parent `AppDaemon` class, and the call will automatically pre-pend the name of the App making the call. The `-D` option of AppDaemon can be used to specify what level of logging is required and the logger objects will work as expected.

### {% linkable_title log() %}

#### {% linkable_title Synopsis %}

```python
log(message, level = "INFO")
```

#### {% linkable_title Returns %}

Nothing

#### {% linkable_title Parameters %}

##### {% linkable_title Message %}

The message to log.

##### {% linkable_title level %}

The log level of the message - takes a string representing the standard logger levels.

#### {% linkable_title Examples %}

```python
self.log("Log Test: Parameter is {}".format(some_variable))
self.log("Log Test: Parameter is {}".format(some_variable), level = "ERROR")
```

### {% linkable_title error() %}

#### {% linkable_title Synopsis %}

```python
error(message, level = "WARNING")
```
#### {% linkable_title Returns %}

Nothing

#### {% linkable_title Parameters %}

##### {% linkable_title Message %}

The message to log.

##### {% linkable_title level %}

The log level of the message - takes a string representing the standard logger levels.

#### {% linkable_title Examples %}

```python
self.error("Some Warning string")
self.error("Some Critical string", level = "CRITICAL")
```

## {% linkable_title Sharing information between Apps %}

Sharing information between different Apps is very simple if required. Each app gets access to a global dictionary stored in a class attribute called `self.global_vars`. Any App can add or read any key as required. This operation is not however threadsafe so some car is needed.

In addition, Apps have access to the entire configuration if required, meaning they can access AppDaemon configuration items as well as parameters from other Apps. To use this, there is a class attribute called `self.config`. It contains a `ConfigParser` object, which is similar in operation to a `Dictionary`. To access any apps parameters, simply reference the ConfigParser object using the Apps name (form the config file) as the first key, and the parameter required as the second, for instance:

```python
other_apps_arg = self.config["some_app"]["some_parameter"].
```

To get AppDaemon's config parameters, use the key "AppDaemon", e.g.:

```python
app_timezone = self.config["AppDaemon"]["time_zone"]
```

And finally, it is also possible to use the AppDaemon as a global area for sharing parameters across Apps. Simply add the required parameters to the AppDaemon section of your config:

```ini
[AppDaemon]
ha_url = <some url>
ha_key = <some key>
...
global_var = hello world
```

Then access it as follows:

```python
my_global_var = conf.config["AppDaemon"]["global_var"]
```

## {% linkable_title Development Workflow %}

Developing Apps is intended to be fairly simple but is an exercise in programming like any other kind of Python programming. As such, it is expected that apps will contain syntax errors and will generate exceptions during the development process. AppDaemon makes it very easy to iterate through the development process as it will automatically reload code that has changed and also will reload code if any of the parameters in the configuration file change as well.

The recommended workflow for development is as follows:

- Open a window and tail the `appdaemon.log` file
- Open a second window and tail the `error.log` file
- Open a third window or the editor of your choice for editing the App

With this setup, you will see that every time you write the file, AppDaemon will log the fact and let you know it has reloaded the App in the `appdaemon.log` file.

If there is an error in the compilation or a runtime error, this will be directed to the `error.log` file to enable you to see the error and correct it. When an error occurs, there will also be a warning message in `appdaemon.log` to tell you to check the error log.

## {% linkable_title Time Travel %}

OK, time travel sadly isn't really possible but it can be very useful when testing Apps. For instance, imagine you have an App that turns a light on every day at sunset. It might be nice to test it without waiting for Sunset - and with AppDaemon's "Time Travel" features you can.

### {% linkable_title Choosing a Start Time %}

Internally, AppDaemon keeps track of it's own time relative to when it was started. This make is possible to start AppDaemon with a different start time and date to the current time. For instance to test that sunset App, start AppDaemon at a time just before sunset and see if it works as expected. To do this, simply use the "-s" argument on AppDaemon's command line. e,g,:

```bash
$ appdaemon -s "2016-06-06 19:16:00"
2016-09-06 17:16:00 INFO AppDaemon Version 1.3.2 starting
2016-09-06 17:16:00 INFO Got initial state
2016-09-06 17:16:00 INFO Loading Module: /export/hass/appdaemon_test/conf/test_apps/sunset.py
...
```

Note the timestamps in the log - AppDaemon believes it is now just before sunset and will process any callbacks appropriately.

### {% linkable_title Speeding things up %}

Some Apps need to run for periods of a day or two for you to test all aspects. This can be time consuming, but Time Travel can also help here in two ways. The first is by speeding up time. To do this, simply use the `-t` option on the command line. This specifies the amount of time a second lasts while time travelling. The default of course is 1 second, but if you change it to `0.1` for instance, AppDaemon will work 10x faster. If you set it to `0`, AppDaemon will work as fast as possible and, depending in your hardware, may be able to get through an entire day in a matter of minutes. Bear in mind however, due to the threaded nature of AppDaemon, when you are running with `-t 0` you may see actual events firing a little later than expected as the rest of the system tries to keep up with the timer. To set the tick time, start AppDaemon as follows:

```bash
$ appdaemon -t 0.1
```

AppDaemon also has an interval flag - think of this as a second multiplier. If the flag is set to 3600 for instance, each tick of the scheduler will jump the time forward by an hour. This is good for covering vast amounts of time quickly but event firing accuracy will suffer as a result. For example:

```bash
$ appdaemon -e 3600
```

### Automatically stopping

AppDaemon can be set to terminate automatically at a specific time. This can be useful if you want to repeatedly rerun a test, for example to test that random values are behaving as expected. Simply specify the end time with the `-e` flag as follows:

```bash
$ appdaemon -e "2016-06-06 10:10:00"
2016-09-06 17:16:00 INFO AppDaemon Version 1.3.2 starting
2016-09-06 17:16:00 INFO Got initial state
2016-09-06 17:16:00 INFO Loading Module: /export/hass/appdaemon_test/conf/test_apps/sunset.py
...
```

The `-e` flag is most useful when used in conjuntion with the -s flag and optionally the `-t` flag. For example, to run from just before sunset, for an hour, as fast as possible:

```bash
$ appdaemon -s "2016-06-06 19:16:00" -s "2016-06-06 20:16:00" -t 0
```


### {% linkable_title A Note on Times %}

Some Apps you write may depend on checking times of events relative to the current time. If you are time travelling this will not work if you use standard python library calls to get the current time and date etc. For this reason, always use the AppDamon supplied `time()`, `date()` and `datetime()` calls, documented earlier. These calls will consult with AppDaemon's internal time rather than the actual time and give you the correct values.
