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gh-150358 Remove unused _complete_fut attribute from asyncio.StreamWriter#150359

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deadlovelll:gh-150358-streamreader-dead-complete_fut
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gh-150358 Remove unused _complete_fut attribute from asyncio.StreamWriter#150359
deadlovelll wants to merge 1 commit into
python:mainfrom
deadlovelll:gh-150358-streamreader-dead-complete_fut

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@deadlovelll deadlovelll commented May 24, 2026 •
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asyncio.StreamWriter.__init__ allocates and resolves a Future and stores it as self._complete_fut, but the attribute is never read anywhere in CPython.

Before:

def __init__(self, transport, protocol, reader, loop):
    self._transport = transport
    self._protocol = protocol
    assert reader is None or isinstance(reader, StreamReader)
    self._reader = reader
    self._loop = loop
    self._complete_fut = self._loop.create_future()
    self._complete_fut.set_result(None)

After:

def __init__(self, transport, protocol, reader, loop):
    self._transport = transport
    self._protocol = protocol
    assert reader is None or isinstance(reader, StreamReader)
    self._reader = reader
    self._loop = loop

The StreamWriter class is used by functions such as: asyncio.open_connection, asyncio.start_server, asyncio.open_unix_connection, asyncio.start_unix_server. So the allocation of an unused future happens on every asyncio network connection

No behavior change.

@bedevere-app bedevere-app Bot mentioned this pull request May 24, 2026
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