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110 lines
4.1 KiB
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110 lines
4.1 KiB
ReStructuredText
Handling Updates
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================
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Calling :doc:`API methods <invoking>` sequentially is cool, but how to react when, for example, a new message arrives?
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This page deals with updates and how to handle such events in Pyrogram. Let's have a look at how they work.
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Defining Updates
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----------------
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First, let's define what are these updates. As hinted already, updates are simply events that happen in your Telegram
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account (incoming messages, new members join, bot button presses, etc...), which are meant to notify you about a new
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specific state that has changed. These updates are handled by registering one or more callback functions in your app
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using :doc:`Handlers <../api/handlers>`.
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Each handler deals with a specific event and once a matching update arrives from Telegram, your registered callback
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function will be called back by the framework and its body executed.
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Registering a Handler
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---------------------
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To explain how handlers work let's have a look at the most used one, the :class:`~pyrogram.MessageHandler`, which will
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be in charge for handling :class:`~pyrogram.Message` updates coming from all around your chats. Every other handler shares
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the same setup logic; you should not have troubles settings them up once you learn from this section.
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Using add_handler()
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-------------------
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The :meth:`~pyrogram.Client.add_handler` method takes any handler instance that wraps around your defined callback
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function and registers it in your Client. Here's a full example that prints out the content of a message as soon as it
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arrives:
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.. code-block:: python
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from pyrogram import Client, MessageHandler
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def my_function(client, message):
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print(message)
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app = Client("my_account")
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my_handler = MessageHandler(my_function)
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app.add_handler(my_handler)
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app.run()
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#. Let's examine these four new pieces. First one: a callback function we defined which accepts two arguments -
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*(client, message)*. This will be the function that gets executed every time a new message arrives and Pyrogram will
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call that function by passing the client instance and the new message instance as argument.
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.. code-block:: python
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def my_function(client, message):
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print(message)
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#. Second one: the :class:`~pyrogram.MessageHandler`. This object tells Pyrogram the function we defined above must
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only handle updates that are in form of a :class:`~pyrogram.Message`:
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.. code-block:: python
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my_handler = MessageHandler(my_function)
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#. Third: the method :meth:`~pyrogram.Client.add_handler`. This method is used to actually register the handler and let
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Pyrogram know it needs to be taken into consideration when new updates arrive and the internal dispatching phase
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begins.
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.. code-block:: python
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app.add_handler(my_handler)
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#. Last one, the :meth:`~pyrogram.Client.run` method. What this does is simply call :meth:`~pyrogram.Client.start` and
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a special method :meth:`~pyrogram.Client.idle` that keeps your main scripts alive until you press ``CTRL+C``; the
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client will be automatically stopped after that.
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.. code-block:: python
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app.run()
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Using Decorators
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----------------
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All of the above will become quite verbose, especially in case you have lots of handlers to register. A much nicer way
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to do so is by decorating your callback function with the :meth:`~pyrogram.Client.on_message` decorator.
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.. code-block:: python
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from pyrogram import Client
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app = Client("my_account")
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@app.on_message()
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def my_handler(client, message):
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print(message)
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app.run()
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.. note::
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Due to how these decorators work in Pyrogram, they will wrap your defined callback function in a tuple consisting of
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``(handler, group)``; this will be the value held by your function identifier (e.g.: *my_function* from the example
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above).
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In case, for some reason, you want to get your own function back after it has been decorated, you need to access
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``my_function[0].callback``, that is, the *callback* field of the *handler* object which is the first element in the
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tuple, accessed by bracket notation *[0]*.
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