discord.ext.tasks – asyncio.Task helpers

New in version 1.1.0.

One of the most common operations when making a bot is having a loop run in the background at a specified interval. This pattern is very common but has a lot of things you need to look out for:

  • How do I handle asyncio.CancelledError?

  • What do I do if the internet goes out?

  • What is the maximum number of seconds I can sleep anyway?

The goal of this discord.py extension is to abstract all these worries away from you.

Recipes

A simple background task in a Cog:

from discord.ext import tasks, commands

class MyCog(commands.Cog):
    def __init__(self):
        self.index = 0
        self.printer.start()

    def cog_unload(self):
        self.printer.cancel()

    @tasks.loop(seconds=5.0)
    async def printer(self):
        print(self.index)
        self.index += 1

Adding an exception to handle during reconnect:

import asyncpg
from discord.ext import tasks, commands

class MyCog(commands.Cog):
    def __init__(self, bot):
        self.bot = bot
        self.data = []
        self.batch_update.add_exception_type(asyncpg.PostgresConnectionError)
        self.batch_update.start()

    def cog_unload(self):
        self.batch_update.cancel()

    @tasks.loop(minutes=5.0)
    async def batch_update(self):
        async with self.bot.pool.acquire() as con:
            # batch update here...
            pass

Looping a certain amount of times before exiting:

from discord.ext import tasks
import discord

@tasks.loop(seconds=5.0, count=5)
async def slow_count():
    print(slow_count.current_loop)

@slow_count.after_loop
async def after_slow_count():
    print('done!')

class MyClient(discord.Client):
    async def setup_hook(self):
        slow_count.start()

Waiting until the bot is ready before the loop starts:

from discord.ext import tasks, commands

class MyCog(commands.Cog):
    def __init__(self, bot):
        self.index = 0
        self.bot = bot
        self.printer.start()

    def cog_unload(self):
        self.printer.cancel()

    @tasks.loop(seconds=5.0)
    async def printer(self):
        print(self.index)
        self.index += 1

    @printer.before_loop
    async def before_printer(self):
        print('waiting...')
        await self.bot.wait_until_ready()

Doing something during cancellation:

from discord.ext import tasks, commands
import asyncio

class MyCog(commands.Cog):
    def __init__(self, bot):
        self.bot = bot
        self._batch = []
        self.lock = asyncio.Lock()
        self.bulker.start()

    async def cog_unload(self):
        self.bulker.cancel()

    async def do_bulk(self):
        # bulk insert data here
        ...

    @tasks.loop(seconds=10.0)
    async def bulker(self):
        async with self.lock:
            await self.do_bulk()

    @bulker.after_loop
    async def on_bulker_cancel(self):
        if self.bulker.is_being_cancelled() and len(self._batch) != 0:
            # if we're cancelled and we have some data left...
            # let's insert it to our database
            await self.do_bulk()

Doing something at a specific time each day:

import datetime
from discord.ext import commands, tasks

utc = datetime.timezone.utc

# If no tzinfo is given then UTC is assumed.
time = datetime.time(hour=8, minute=30, tzinfo=utc)

class MyCog(commands.Cog):
    def __init__(self, bot):
        self.bot = bot
        self.my_task.start()

    def cog_unload(self):
        self.my_task.cancel()

    @tasks.loop(time=time)
    async def my_task(self):
        print("My task is running!")

Doing something at multiple specific times each day:

import datetime
from discord.ext import commands, tasks

utc = datetime.timezone.utc

# If no tzinfo is given then UTC is assumed.
times = [
    datetime.time(hour=8, tzinfo=utc),
    datetime.time(hour=12, minute=30, tzinfo=utc),
    datetime.time(hour=16, minute=40, second=30, tzinfo=utc)
]

class MyCog(commands.Cog):
    def __init__(self, bot):
        self.bot = bot
        self.my_task.start()

    def cog_unload(self):
        self.my_task.cancel()

    @tasks.loop(time=times)
    async def my_task(self):
        print("My task is running!")

API Reference

Attributes
Methods
class discord.ext.tasks.Loop

A background task helper that abstracts the loop and reconnection logic for you.

The main interface to create this is through loop().

@after_loop

A decorator that registers a coroutine to be called after the loop finishes running.

The coroutine must take no arguments (except self in a class context).

Note

This coroutine is called even during cancellation. If it is desirable to tell apart whether something was cancelled or not, check to see whether is_being_cancelled() is True or not.

Parameters

coro (coroutine) – The coroutine to register after the loop finishes.

Raises

TypeError – The function was not a coroutine.

@before_loop

A decorator that registers a coroutine to be called before the loop starts running.

This is useful if you want to wait for some bot state before the loop starts, such as discord.Client.wait_until_ready().

The coroutine must take no arguments (except self in a class context).

Changed in version 2.0: Calling stop() in this coroutine will stop the loop before the initial iteration is run.

Parameters

coro (coroutine) – The coroutine to register before the loop runs.

Raises

TypeError – The function was not a coroutine.

@error

A decorator that registers a coroutine to be called if the task encounters an unhandled exception.

The coroutine must take only one argument the exception raised (except self in a class context).

By default this logs to the library logger however it could be overridden to have a different implementation.

New in version 1.4.

Changed in version 2.0: Instead of writing to sys.stderr, the library’s logger is used.

Parameters

coro (coroutine) – The coroutine to register in the event of an unhandled exception.

Raises

TypeError – The function was not a coroutine.

property seconds

Read-only value for the number of seconds between each iteration. None if an explicit time value was passed instead.

New in version 2.0.

Type

Optional[float]

property minutes

Read-only value for the number of minutes between each iteration. None if an explicit time value was passed instead.

New in version 2.0.

Type

Optional[float]

property hours

Read-only value for the number of hours between each iteration. None if an explicit time value was passed instead.

New in version 2.0.

Type

Optional[float]

property time

Read-only list for the exact times this loop runs at. None if relative times were passed instead.

New in version 2.0.

Type

Optional[List[datetime.time]]

property current_loop

The current iteration of the loop.

Type

int

property next_iteration

When the next iteration of the loop will occur.

New in version 1.3.

Type

Optional[datetime.datetime]

await __call__(*args, **kwargs)

This function is a coroutine.

Calls the internal callback that the task holds.

New in version 1.6.

Parameters

  • *args – The arguments to use.

  • **kwargs – The keyword arguments to use.

start(*args, **kwargs)

Starts the internal task in the event loop.

Parameters

  • *args – The arguments to use.

  • **kwargs – The keyword arguments to use.

Raises

RuntimeError – A task has already been launched and is running.

Returns

The task that has been created.

Return type

asyncio.Task

stop()

Gracefully stops the task from running.

Unlike cancel(), this allows the task to finish its current iteration before gracefully exiting.

Note

If the internal function raises an error that can be handled before finishing then it will retry until it succeeds.

If this is undesirable, either remove the error handling before stopping via clear_exception_types() or use cancel() instead.

Changed in version 2.0: Calling this method in before_loop() will stop the loop before the initial iteration is run.

New in version 1.2.

cancel()

Cancels the internal task, if it is running.

restart(*args, **kwargs)

A convenience method to restart the internal task.

Note

Due to the way this function works, the task is not returned like start().

Parameters

  • *args – The arguments to use.

  • **kwargs – The keyword arguments to use.

add_exception_type(*exceptions)

Adds exception types to be handled during the reconnect logic.

By default the exception types handled are those handled by discord.Client.connect(), which includes a lot of internet disconnection errors.

This function is useful if you’re interacting with a 3rd party library that raises its own set of exceptions.

Parameters

*exceptions (Type[BaseException]) – An argument list of exception classes to handle.

Raises

TypeError – An exception passed is either not a class or not inherited from BaseException.

clear_exception_types()

Removes all exception types that are handled.

Note

This operation obviously cannot be undone!

remove_exception_type(*exceptions)

Removes exception types from being handled during the reconnect logic.

Parameters

*exceptions (Type[BaseException]) – An argument list of exception classes to handle.

Returns

Whether all exceptions were successfully removed.

Return type

bool

get_task()

Optional[asyncio.Task]: Fetches the internal task or None if there isn’t one running.

is_being_cancelled()

Whether the task is being cancelled.

failed()

bool: Whether the internal task has failed.

New in version 1.2.

is_running()

bool: Check if the task is currently running.

New in version 1.4.

change_interval(*, seconds=0, minutes=0, hours=0, time=...)

Changes the interval for the sleep time.

New in version 1.2.

Parameters

  • seconds (float) – The number of seconds between every iteration.

  • minutes (float) – The number of minutes between every iteration.

  • hours (float) – The number of hours between every iteration.

  • time (Union[datetime.time, Sequence[datetime.time]]) –

    The exact times to run this loop at. Either a non-empty list or a single value of datetime.time should be passed. This cannot be used in conjunction with the relative time parameters.

    New in version 2.0.

    Note

    Duplicate times will be ignored, and only run once.

Raises

  • ValueError – An invalid value was given.

  • TypeError – An invalid value for the time parameter was passed, or the time parameter was passed in conjunction with relative time parameters.

@discord.ext.tasks.loop(*, seconds=..., minutes=..., hours=..., time=..., count=None, reconnect=True)

A decorator that schedules a task in the background for you with optional reconnect logic. The decorator returns a Loop.

Parameters

  • seconds (float) – The number of seconds between every iteration.

  • minutes (float) – The number of minutes between every iteration.

  • hours (float) – The number of hours between every iteration.

  • time (Union[datetime.time, Sequence[datetime.time]]) –

    The exact times to run this loop at. Either a non-empty list or a single value of datetime.time should be passed. Timezones are supported. If no timezone is given for the times, it is assumed to represent UTC time.

    This cannot be used in conjunction with the relative time parameters.

    Note

    Duplicate times will be ignored, and only run once.

    New in version 2.0.

  • count (Optional[int]) – The number of loops to do, None if it should be an infinite loop.

  • reconnect (bool) – Whether to handle errors and restart the task using an exponential back-off algorithm similar to the one used in discord.Client.connect().

Raises

  • ValueError – An invalid value was given.

  • TypeError – The function was not a coroutine, an invalid value for the time parameter was passed, or time parameter was passed in conjunction with relative time parameters.