diff options
| -rw-r--r-- | Doc/library/contextlib.rst | 18 | ||||
| -rw-r--r-- | Lib/contextlib.py | 8 | ||||
| -rw-r--r-- | Lib/test/test_contextlib_async.py | 14 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Library/2020-08-14-00-39-04.bpo-41543.RpcRjb.rst | 1 |
4 files changed, 39 insertions, 2 deletions
diff --git a/Doc/library/contextlib.rst b/Doc/library/contextlib.rst index d5a1068..91edbba 100644 --- a/Doc/library/contextlib.rst +++ b/Doc/library/contextlib.rst @@ -243,8 +243,26 @@ Functions and classes provided: with cm as file: # Perform processing on the file + It can also be used as a stand-in for + :ref:`asynchronous context managers <async-context-managers>`:: + + async def send_http(session=None): + if not session: + # If no http session, create it with aiohttp + cm = aiohttp.ClientSession() + else: + # Caller is responsible for closing the session + cm = nullcontext(session) + + async with cm as session: + # Send http requests with session + .. versionadded:: 3.7 + .. versionchanged:: 3.10 + :term:`asynchronous context manager` support was added. + + .. function:: suppress(*exceptions) diff --git a/Lib/contextlib.py b/Lib/contextlib.py index 56b4968..a0b523c 100644 --- a/Lib/contextlib.py +++ b/Lib/contextlib.py @@ -704,7 +704,7 @@ class AsyncExitStack(_BaseExitStack, AbstractAsyncContextManager): return received_exc and suppressed_exc -class nullcontext(AbstractContextManager): +class nullcontext(AbstractContextManager, AbstractAsyncContextManager): """Context manager that does no additional processing. Used as a stand-in for a normal context manager, when a particular @@ -723,3 +723,9 @@ class nullcontext(AbstractContextManager): def __exit__(self, *excinfo): pass + + async def __aenter__(self): + return self.enter_result + + async def __aexit__(self, *excinfo): + pass diff --git a/Lib/test/test_contextlib_async.py b/Lib/test/test_contextlib_async.py index 109807d..290ef05 100644 --- a/Lib/test/test_contextlib_async.py +++ b/Lib/test/test_contextlib_async.py @@ -1,5 +1,7 @@ import asyncio -from contextlib import aclosing, asynccontextmanager, AbstractAsyncContextManager, AsyncExitStack +from contextlib import ( + asynccontextmanager, AbstractAsyncContextManager, + AsyncExitStack, nullcontext, aclosing) import functools from test import support import unittest @@ -537,5 +539,15 @@ class TestAsyncExitStack(TestBaseExitStack, unittest.TestCase): self.assertIsInstance(inner_exc.__context__, ZeroDivisionError) +class TestAsyncNullcontext(unittest.TestCase): + @_async_test + async def test_async_nullcontext(self): + class C: + pass + c = C() + async with nullcontext(c) as c_in: + self.assertIs(c_in, c) + + if __name__ == '__main__': unittest.main() diff --git a/Misc/NEWS.d/next/Library/2020-08-14-00-39-04.bpo-41543.RpcRjb.rst b/Misc/NEWS.d/next/Library/2020-08-14-00-39-04.bpo-41543.RpcRjb.rst new file mode 100644 index 0000000..753dc76 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2020-08-14-00-39-04.bpo-41543.RpcRjb.rst @@ -0,0 +1 @@ +Add async context manager support for contextlib.nullcontext. |