More on Updates

Here we’ll show some advanced usages when working with update handlers and filters.

Handler Groups

If you register handlers with overlapping (conflicting) filters, only the first one is executed and any other handler will be ignored. This is intended by design.

In order to handle the very same update more than once, you have to register your handler in a different dispatching group. Dispatching groups hold one or more handlers and are processed sequentially, they are identified by a number (number 0 being the default) and sorted, that is, a lower group number has a higher priority:

For example, take these two handlers:

@app.on_message(Filters.text | Filters.sticker)
def text_or_sticker(client, message):
    print("Text or Sticker")


@app.on_message(Filters.text)
def just_text(client, message):
    print("Just Text")

Here, just_text is never executed because text_or_sticker, which has been registered first, already handles texts (Filters.text is shared and conflicting). To enable it, register the handler using a different group:

@app.on_message(Filters.text, group=1)
def just_text(client, message):
    print("Just Text")

Or, if you want just_text to be executed before text_or_sticker (note -1, which is less than 0):

@app.on_message(Filters.text, group=-1)
def just_text(client, message):
    print("Just Text")

With add_handler() (without decorators) the same can be achieved with:

app.add_handler(MessageHandler(just_text, Filters.text), -1)

Update propagation

Registering multiple handlers, each in a different group, becomes useful when you want to handle the same update more than once. Any incoming update will be sequentially processed by all of your registered functions by respecting the groups priority policy described above. Even in case any handler raises an unhandled exception, Pyrogram will still continue to propagate the same update to the next groups until all the handlers are done. Example:

@app.on_message(Filters.private)
def _(client, message):
    print(0)


@app.on_message(Filters.private, group=1)
def _(client, message):
    raise Exception("Unhandled exception!")  # Simulate an unhandled exception


@app.on_message(Filters.private, group=2)
def _(client, message):
    print(2)

All these handlers will handle the same kind of messages, that are, messages sent or received in private chats. The output for each incoming update will therefore be:

0
Exception: Unhandled exception!
2

Stop Propagation

In order to prevent further propagation of an update in the dispatching phase, you can do one of the following:

  • Call the update’s bound-method .stop_propagation() (preferred way).

  • Manually raise StopPropagation exception (more suitable for raw updates only).

Note

Internally, the propagation is stopped by handling a custom exception. .stop_propagation() is just an elegant and intuitive way to raise StopPropagation; this also means that any code coming after calling the method won’t be executed as your function just raised an exception to signal the dispatcher not to propagate the update anymore.

Example with stop_propagation():

@app.on_message(Filters.private)
def _(client, message):
    print(0)


@app.on_message(Filters.private, group=1)
def _(client, message):
    print(1)
    message.stop_propagation()


@app.on_message(Filters.private, group=2)
def _(client, message):
    print(2)

Example with raise StopPropagation:

from pyrogram import StopPropagation

@app.on_message(Filters.private)
def _(client, message):
    print(0)


@app.on_message(Filters.private, group=1)
def _(client, message):
    print(1)
    raise StopPropagation


@app.on_message(Filters.private, group=2)
def _(client, message):
    print(2)

Each handler is registered in a different group, but the handler in group number 2 will never be executed because the propagation was stopped earlier. The output of both (equivalent) examples will be:

0
1

Continue Propagation

As opposed to stopping the update propagation and also as an alternative to the handler groups, you can signal the internal dispatcher to continue the update propagation within the same group despite having conflicting filters in the next registered handler. This allows you to register multiple handlers with overlapping filters in the same group; to let the dispatcher process the next handler you can do one of the following in each handler you want to grant permission to continue:

  • Call the update’s bound-method .continue_propagation() (preferred way).

  • Manually raise ContinuePropagation exception (more suitable for raw updates only).

Note

Internally, the propagation is continued by handling a custom exception. .continue_propagation() is just an elegant and intuitive way to raise ContinuePropagation; this also means that any code coming after calling the method won’t be executed as your function just raised an exception to signal the dispatcher to continue with the next available handler.

Example with continue_propagation():

@app.on_message(Filters.private)
def _(client, message):
    print(0)
    message.continue_propagation()


@app.on_message(Filters.private)
def _(client, message):
    print(1)
    message.continue_propagation()


@app.on_message(Filters.private)
def _(client, message):
    print(2)

Example with raise ContinuePropagation:

from pyrogram import ContinuePropagation

@app.on_message(Filters.private)
def _(client, message):
    print(0)
    raise ContinuePropagation


@app.on_message(Filters.private)
def _(client, message):
    print(1)
    raise ContinuePropagation


@app.on_message(Filters.private)
def _(client, message):
    print(2)

Three handlers are registered in the same group, and all of them will be executed because the propagation was continued in each handler (except in the last one, where is useless to do so since there is no more handlers after). The output of both (equivalent) examples will be:

0
1
2