Function open_nursery

src/trio/_core/_run.py:1152–1188

Returns an async context manager which must be used to create a new `Nursery`. It does not block on entry; on exit it blocks until all child tasks have exited. If no child tasks are running on exit, it will insert a schedule point (but no cancellation point) - equivalent to :fun

(
    strict_exception_groups: bool | None = None,
)

def open_nursery(
    strict_exception_groups: bool | None = None,
) -> AbstractAsyncContextManager[Nursery]:
    """Returns an async context manager which must be used to create a
    new `Nursery`.

    It does not block on entry; on exit it blocks until all child tasks
    have exited. If no child tasks are running on exit, it will insert a
    schedule point (but no cancellation point) - equivalent to
    :func:`trio.lowlevel.cancel_shielded_checkpoint`. This means a nursery
    is never the source of a cancellation exception, it only propagates it
    from sub-tasks.

    Args:
      strict_exception_groups (bool): Unless set to False, even a single raised exception
          will be wrapped in an exception group. If not specified, uses the value passed
          to :func:`run`, which defaults to true. Setting it to False will be deprecated
          and ultimately removed in a future version of Trio.

    """
    # only warn if explicitly set to falsy, not if we get it from the global context.
    if strict_exception_groups is not None and not strict_exception_groups:
        warn_deprecated(
            "open_nursery(strict_exception_groups=False)",
            version="0.25.0",
            issue=2929,
            instead=(
                "the default value of True and rewrite exception handlers to handle ExceptionGroups. "
                "See https://trio.readthedocs.io/en/stable/reference-core.html#designing-for-multiple-errors"
            ),
            use_triodeprecationwarning=True,
        )

    if strict_exception_groups is None:
        strict_exception_groups = GLOBAL_RUN_CONTEXT.runner.strict_exception_groups

    return NurseryManager(strict_exception_groups=strict_exception_groups)


@final