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# CommandHandler

class telegram.ext.CommandHandler(command, callback, filters=None, block=True, has_args=None)

  Bases: `telegram.ext.BaseHandler`

  Handler class to handle Telegram commands.

  Commands are Telegram messages that start with a `telegram.MessageEntity.BOT_COMMAND` (so with `/`, optionally followed by an `@` and the bot’s name and/or some additional text). The handler will add a `list` to the `CallbackContext` named `CallbackContext.args`. It will contain a list of strings, which is the text following the command split on single or consecutive whitespace characters.

  By default, the handler listens to messages as well as edited messages. To change this behavior use `~filters.UpdateType.EDITED_MESSAGE` in the filter argument.

  Note

  `CommandHandler` does not handle (edited) channel posts and does not handle commands that are part of a caption. Please use `MessageHandler` with a suitable combination of filters (e.g. `telegram.ext.filters.UpdateType.CHANNEL_POSTS`, `telegram.ext.filters.CAPTION` and `telegram.ext.filters.Regex`) to handle those messages.

  Note

  If you want to support a different entity in the beginning, e.g. if a command message is wrapped in a `telegram.MessageEntity.CODE`, use the `telegram.ext.PrefixHandler`.

  Warning

  When setting `block` to `False`, you cannot rely on adding custom attributes to `telegram.ext.CallbackContext`. See its docs for more info.

  Examples

  - Timer Bot

  - Error Handler Bot

  Available In

  `telegram.ext.Application.handlers`

  Changed in version 20.0:

  - Renamed the attribute `command` to `commands`, which now is always a `frozenset`

  - Updating the commands this handler listens to is no longer possible.

  Parameters:

    - command (`str` | Collection[`str`]) – The command or list of commands this handler should listen for. Case-insensitive. Limitations are the same as for `telegram.BotCommand.command`.

    - callback (coroutine function) –

      The callback function for this handler. Will be called when `check_update()` has determined that an update should be processed by this handler. Callback signature:

          async def callback(update: Update, context: CallbackContext)

      The return value of the callback is usually ignored except for the special case of `telegram.ext.ConversationHandler`.

    - filters (`telegram.ext.filters.BaseFilter`, optional) – A filter inheriting from `telegram.ext.filters.BaseFilter`. Standard filters can be found in `telegram.ext.filters`. Filters can be combined using bitwise operators (`&` for `and`, `|` for `or`, `~` for `not`)

    - block (`bool`, optional) –

      Determines whether the return value of the callback should be awaited before processing the next handler in `telegram.ext.Application.process_update()`. Defaults to `True`.

      See also

      Concurrency

    - has_args (`bool` | `int`, optional) –

      Determines whether the command handler should process the update or not. If `True`, the handler will process any non-zero number of args. If `False`, the handler will only process if there are no args. if `int`, the handler will only process if there are exactly that many args. Defaults to `None`, which means the handler will process any or no args.

      Added in version 20.5.

  Raises:

    ValueError – When the command is too long or has illegal chars.

  commands

    The set of commands this handler should listen for.

    Type:

      frozenset[`str`]

  callback

    The callback function for this handler.

    Type:

      coroutine function

  filters

    Optional. Only allow updates with these filters.

    Type:

      `telegram.ext.filters.BaseFilter`

  block

    Determines whether the return value of the callback should be awaited before processing the next handler in `telegram.ext.Application.process_update()`.

    Type:

      `bool`

  has_args

    Optional argument, otherwise all implementations of `CommandHandler` will break. Defaults to `None`, which means the handler will process any args or no args.

    Added in version 20.5.

    Type:

      `bool` | `int` | None

  check_update(update)

    Determines whether an update should be passed to this handler’s `callback`.

    Parameters:

      update (`telegram.Update` | `object`) – Incoming update.

    Returns:

      The list of args for the handler.

    Return type:

      `list`

  collect_additional_context(context, update, application, check_result)

    Add text after the command to `CallbackContext.args` as list, split on single whitespaces and add output of data filters to `CallbackContext` as well.