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bpo-8110: Refactor platform detection in subprocess (GH-9053)
Check for functionality via imports rather than checking sys.platform specifically for Windows
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‎Lib/subprocess.py

Lines changed: 56 additions & 55 deletions
Original file line numberDiff line numberDiff line change
@@ -41,18 +41,56 @@
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then returns a (exitcode, output) tuple
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"""
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import sys
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_mswindows = (sys.platform == "win32")
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import builtins
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import errno
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import io
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import os
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import time
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import signal
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import builtins
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import sys
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import threading
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import warnings
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import errno
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from time import monotonic as _time
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__all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call", "getstatusoutput",
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"getoutput", "check_output", "run", "CalledProcessError", "DEVNULL",
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"SubprocessError", "TimeoutExpired", "CompletedProcess"]
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# NOTE: We intentionally exclude list2cmdline as it is
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# considered an internal implementation detail. issue10838.
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try:
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import msvcrt
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import _winapi
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_mswindows = True
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except ModuleNotFoundError:
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_mswindows = False
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import _posixsubprocess
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import select
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import selectors
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else:
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from _winapi import (CREATE_NEW_CONSOLE, CREATE_NEW_PROCESS_GROUP,
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STD_INPUT_HANDLE, STD_OUTPUT_HANDLE,
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STD_ERROR_HANDLE, SW_HIDE,
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STARTF_USESTDHANDLES, STARTF_USESHOWWINDOW,
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ABOVE_NORMAL_PRIORITY_CLASS, BELOW_NORMAL_PRIORITY_CLASS,
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HIGH_PRIORITY_CLASS, IDLE_PRIORITY_CLASS,
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NORMAL_PRIORITY_CLASS, REALTIME_PRIORITY_CLASS,
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CREATE_NO_WINDOW, DETACHED_PROCESS,
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CREATE_DEFAULT_ERROR_MODE, CREATE_BREAKAWAY_FROM_JOB)
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__all__.extend(["CREATE_NEW_CONSOLE", "CREATE_NEW_PROCESS_GROUP",
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"STD_INPUT_HANDLE", "STD_OUTPUT_HANDLE",
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"STD_ERROR_HANDLE", "SW_HIDE",
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"STARTF_USESTDHANDLES", "STARTF_USESHOWWINDOW",
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"STARTUPINFO",
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"ABOVE_NORMAL_PRIORITY_CLASS", "BELOW_NORMAL_PRIORITY_CLASS",
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"HIGH_PRIORITY_CLASS", "IDLE_PRIORITY_CLASS",
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"NORMAL_PRIORITY_CLASS", "REALTIME_PRIORITY_CLASS",
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"CREATE_NO_WINDOW", "DETACHED_PROCESS",
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"CREATE_DEFAULT_ERROR_MODE", "CREATE_BREAKAWAY_FROM_JOB"])
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# Exception classes used by this module.
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class SubprocessError(Exception): pass
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@@ -123,9 +161,6 @@ def stdout(self, value):
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if _mswindows:
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import threading
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import msvcrt
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import _winapi
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class STARTUPINFO:
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def __init__(self, *, dwFlags=0, hStdInput=None, hStdOutput=None,
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hStdError=None, wShowWindow=0, lpAttributeList=None):
@@ -148,53 +183,6 @@ def copy(self):
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wShowWindow=self.wShowWindow,
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lpAttributeList=attr_list)
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else:
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import _posixsubprocess
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import select
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import selectors
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import threading
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# When select or poll has indicated that the file is writable,
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# we can write up to _PIPE_BUF bytes without risk of blocking.
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# POSIX defines PIPE_BUF as >= 512.
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_PIPE_BUF = getattr(select, 'PIPE_BUF', 512)
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# poll/select have the advantage of not requiring any extra file
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# descriptor, contrarily to epoll/kqueue (also, they require a single
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# syscall).
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if hasattr(selectors, 'PollSelector'):
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_PopenSelector = selectors.PollSelector
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else:
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_PopenSelector = selectors.SelectSelector
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__all__ = ["Popen", "PIPE", "STDOUT", "call", "check_call", "getstatusoutput",
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"getoutput", "check_output", "run", "CalledProcessError", "DEVNULL",
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"SubprocessError", "TimeoutExpired", "CompletedProcess"]
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# NOTE: We intentionally exclude list2cmdline as it is
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# considered an internal implementation detail. issue10838.
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if _mswindows:
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from _winapi import (CREATE_NEW_CONSOLE, CREATE_NEW_PROCESS_GROUP,
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STD_INPUT_HANDLE, STD_OUTPUT_HANDLE,
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STD_ERROR_HANDLE, SW_HIDE,
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STARTF_USESTDHANDLES, STARTF_USESHOWWINDOW,
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ABOVE_NORMAL_PRIORITY_CLASS, BELOW_NORMAL_PRIORITY_CLASS,
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HIGH_PRIORITY_CLASS, IDLE_PRIORITY_CLASS,
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NORMAL_PRIORITY_CLASS, REALTIME_PRIORITY_CLASS,
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CREATE_NO_WINDOW, DETACHED_PROCESS,
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CREATE_DEFAULT_ERROR_MODE, CREATE_BREAKAWAY_FROM_JOB)
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__all__.extend(["CREATE_NEW_CONSOLE", "CREATE_NEW_PROCESS_GROUP",
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"STD_INPUT_HANDLE", "STD_OUTPUT_HANDLE",
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"STD_ERROR_HANDLE", "SW_HIDE",
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"STARTF_USESTDHANDLES", "STARTF_USESHOWWINDOW",
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"STARTUPINFO",
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"ABOVE_NORMAL_PRIORITY_CLASS", "BELOW_NORMAL_PRIORITY_CLASS",
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"HIGH_PRIORITY_CLASS", "IDLE_PRIORITY_CLASS",
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"NORMAL_PRIORITY_CLASS", "REALTIME_PRIORITY_CLASS",
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"CREATE_NO_WINDOW", "DETACHED_PROCESS",
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"CREATE_DEFAULT_ERROR_MODE", "CREATE_BREAKAWAY_FROM_JOB"])
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199187
class Handle(int):
200188
closed = False
@@ -215,6 +203,19 @@ def __repr__(self):
215203

216204
__del__ = Close
217205
__str__ = __repr__
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else:
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# When select or poll has indicated that the file is writable,
208+
# we can write up to _PIPE_BUF bytes without risk of blocking.
209+
# POSIX defines PIPE_BUF as >= 512.
210+
_PIPE_BUF = getattr(select, 'PIPE_BUF', 512)
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212+
# poll/select have the advantage of not requiring any extra file
213+
# descriptor, contrarily to epoll/kqueue (also, they require a single
214+
# syscall).
215+
if hasattr(selectors, 'PollSelector'):
216+
_PopenSelector = selectors.PollSelector
217+
else:
218+
_PopenSelector = selectors.SelectSelector
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# This lists holds Popen instances for which the underlying process had not

‎Misc/NEWS.d/next/Library/2018-09-03-23-54-35.bpo-8110.FExWI_.rst

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,2 @@
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Refactored :mod:`subprocess` to check for Windows-specific modules rather
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than ``sys.platform == 'win32'``.

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