Function is_asyncio_available

scrapy/utils/asyncio.py:34–92

Check if it's possible to call asyncio code that relies on the asyncio event loop. .. versionadded:: 2.14 This function returns ``True`` if there is a running asyncio event loop. If there is no such loop, it returns ``True`` if the Twisted reactor that is installed is :class:`~

()

def is_asyncio_available() -> bool:
    class="st">"""Check if it&class="cm">#x27;s possible to call asyncio code that relies on the asyncio event loop.

    .. versionadded:: 2.14

    This function returns ``True`` if there is a running asyncio event loop. If
    there is no such loop, it returns ``True`` if the Twisted reactor that is
    installed is
    :class:`~twisted.internet.asyncioreactor.AsyncioSelectorReactor`, returns
    ``False`` if a different reactor is installed, and raises a
    :exc:`RuntimeError` if no reactor is installed.

    Code that doesn&class="cm">#x27;t directly require a Twisted reactor should use this
    function while code that requires
    :class:`~twisted.internet.asyncioreactor.AsyncioSelectorReactor` should use
    :func:`~scrapy.utils.reactor.is_asyncio_reactor_installed`.

    When this returns ``True``, an asyncio loop is installed and used by
    Scrapy. It&class="cm">#x27;s possible to call functions that require it, such as
    :func:`asyncio.sleep`, and await on :class:`asyncio.Future` objects in
    Scrapy-related code.

    When this returns ``False``, a non-asyncio Twisted reactor is installed.
    It&class="cm">#x27;s not possible to use asyncio features that require an asyncio event
    loop or await on :class:`asyncio.Future` objects in Scrapy-related code,
    but it&class="cm">#x27;s possible to await on :class:`~twisted.internet.defer.Deferred`
    objects.

    .. note:: As this function uses :func:`asyncio.get_running_loop()`, it will
        only detect the event loop if called in the same thread and from the
        code that runs inside that loop (this shouldn&class="cm">#x27;t be a problem when
        calling it from code such as spiders and Scrapy components, if Scrapy
        is run using one of the supported ways).

    .. versionchanged:: 2.15.0
        This function now also returns ``True`` if there is a running asyncio
        loop, even if no Twisted reactor is installed.
    class="st">"""

    class="cm"># Check if there is a running asyncio loop.
    class="cm"># Can't easily check for an installed but not running one, and if we
    class="cm"># checked that there could be false positives due to some 3rd-party code
    class="cm"># installing it as a side effect (e.g. by calling get_event_loop()).
    try:
        asyncio.get_running_loop()
    except RuntimeError:
        pass
    else:
        return True

    class="cm"># Check if there is an installed asyncio reactor (it doesn't need to be
    class="cm"># running).
    if not is_reactor_installed():
        raise RuntimeError(
            class="st">"is_asyncio_available() called without an installed reactor"
            class="st">" or running asyncio loop."
        )