Use result of func paramter in handler.

[byehack]

def fn(message):
    return ", Word!"

@bot.message_handler(func=fn)
async def hndler(message, func_result):
    print("Hello"+func_result)

[coder2020official]

Here are my points about it:

• Func should return True/False. If False was returned, then handler won't run. If True is returned, then handler will run. What is the point of getting True always(you can return other values but purpose is to create lambda filters)?
• If you need to pass something to handlers, I'd recommend taking a look at middlewares

[byehack]

• (you can return other values but purpose is to create lambda filters)

Some times the filter function is longer than is to fit lambda.

def fn(message):
    if is_text_is_link(message.text):
        content =  download(message.text).content
        filtered_content = filter_content(content)
        if is_ok(filtered_content): return True

@bot.message_handler(func=fn)
async def hndler(message):
    content =  download(message.text).content
    filtered_content = filter_content(content)
    bot.send_message(filtered_content)

by accept func paremeter result in handler:

def fn(message):
    if is_text_is_link(message.text):
        content =  download(message.text).content
        filtered_content = filter_content(content)
        if is_ok(filtered_content): return filtered_content

@bot.message_handler(func=fn)
async def hndler(message, func_result):
    bot.send_message(func_result)

this avoid duplicate processing. (more efficient)

• Func should return True/False.

No, Func result most not always be bool, it can return type of Any according to here:

pyTelegramBotAPI/telebot/__init__.py

Line 5859 in b841fc1

return filter_value(message)

I think here is should try to start supporting it.

pyTelegramBotAPI/telebot/__init__.py

Line 5929 in b841fc1

elif "data" in params:

[coder2020official]

The purpose of it is to return true false eventhough it allows to pass other data types; Take a look at custom filters. The purpose of custom filters is to create such "long" filter functions.

[byehack]

The purpose of custom filters is to create such "long" filter functions.

:/ still duplicate download and duplicate processing.

class cust(telebot.custom_filters.SimpleCustomFilter):
    key='is_my_link'
    @staticmethod
    def check(message: telebot.types.Message):
        if is_text_is_link(message.text):
            content =  download(message.text).content
            filtered_content = filter_content(content)
            if is_ok(filtered_content): return True
	
bot.add_custom_filter(cust())

@bot.message_handler(is_my_link=True)
def hndler(message):
    content =  download(message.text).content
    filtered_content = filter_content(content)
    bot.send_message(filtered_content)

[coder2020official]

Then create a class-based middleware, create a check there , and add download to data.

[byehack]

:/ why just not use clear code and simple way?

[byehack]

The purpose can change.
and also it is backward compatible!

[coder2020official]

Using middlewares you can achieve that easily;
Do it through middlewares

[Cub11k]

@byehack you totally misunderstood the concept :)
Any arguments in the decorator are filters, they are supposed to define whether to execute this handler or skip it and try others. Their purpose won't ever change

To pass any extra parameters to the handler you should use middleware