Updated Types of Handlers (markdown)

Joscha Götzer 2017-12-27 23:19:48 +01:00
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A `Handler` is an instance derived from the base class [telegram.ext.Handler](https://python-telegram-bot.readthedocs.io/en/latest/telegram.ext.handler.html#telegram.ext.Handler) which is responsible for the routing of different kinds of updates (text, audio, inlinequery, button presses, ...) to their _corresponding callback function_ in your code.
For example, if you want your bot to respond to the command `/start`, you can use a [CommandHandler](https://python-telegram-bot.readthedocs.io/en/latest/telegram.ext.commandhandler.html) that maps the input to a callback named `my_start_callback`:
For example, if you want your bot to respond to the command `/start`, you can use a [CommandHandler](https://python-telegram-bot.readthedocs.io/en/latest/telegram.ext.commandhandler.html) that maps this user input to a callback named `start_callback`:
```
def my_start_callback(bot, update):
def start_callback(bot, update):
update.message.reply_text("Welcome to my awesome bot!")
...
dispatcher.add_handler(CommandHandler("start", my_start_callback))```
dispatcher.add_handler(CommandHandler("start", start_callback))```
## CommandHandlers with arguments
It is also possible to work with parameters for commands offered by your bot. Let's extend the `start_callback` with some arguments so that the user can provide additional information in the same step:
```
def start_callback(bot, update, args):
user_says = " ".join(args)
update.message.reply_text("You said: " + user_says)
...
dispatcher.add_handler(CommandHandler("start", start_callback, pass_args=True))```
Sending "/start Hello World!" to your bot will now split everything after /start separated by the space character into a list of words and pass it on to the `args` parameter of `start_callback`: `["Hello", "World!"]`. We join these chunks together by calling `" ".join(args)` and echo the resulting string back to the user.
### Deep-Linking start parameters
The argument passing described above works exactly the same when the user clicks on a deeply linked start URL, like this one:
https://t.me/roolsbot?start=Hello%20World!
Clicking this link will open your Telegram Client and show a big START button. When it is pressed, the URL parameters "Hello World!" will be passed on to the `args` of your /start callback.
## Pattern matching: The RegexHandler
For more complex inputs you can employ the [telegram.ext.RegexHandler](https://python-telegram-bot.readthedocs.io/en/latest/telegram.ext.regexhandler.html), which internally uses the `re`-module to match textual user input with a supplied pattern.
A quick example:
```
```
Keep in mind that for extracting URLs, #Hashtags, @Mentions, and other Telegram entities, there's no need to parse them with a `RegexHandler` because the Bot API already sends them to us with every update. Refer to [this snippet](https://github.com/python-telegram-bot/python-telegram-bot/wiki/Code-snippets#message-entities) to learn how to work with entities instead.
To learn about all