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Diffstat (limited to 'Doc/library/subprocess.rst')
| -rw-r--r-- | Doc/library/subprocess.rst | 23 |
1 files changed, 13 insertions, 10 deletions
diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst index 1c8aafd..59ee13f 100644 --- a/Doc/library/subprocess.rst +++ b/Doc/library/subprocess.rst @@ -284,7 +284,7 @@ are able to handle the less common cases not covered by the convenience functions. -.. class:: Popen(args, bufsize=0, executable=None, stdin=None, stdout=None, \ +.. class:: Popen(args, bufsize=-1, executable=None, stdin=None, stdout=None, \ stderr=None, preexec_fn=None, close_fds=True, shell=False, \ cwd=None, env=None, universal_newlines=False, \ startupinfo=None, creationflags=0, restore_signals=True, \ @@ -356,17 +356,20 @@ functions. untrusted input. See the warning under :ref:`frequently-used-arguments` for details. - *bufsize*, if given, has the same meaning as the corresponding argument to the - built-in open() function: :const:`0` means unbuffered, :const:`1` means line - buffered, any other positive value means use a buffer of (approximately) that - size. A negative *bufsize* means to use the system default, which usually means - fully buffered. The default value for *bufsize* is :const:`0` (unbuffered). + *bufsize* will be supplied as the corresponding argument to the :meth:`io.open` + function when creating the stdin/stdout/stderr pipe file objects: + :const:`0` means unbuffered (read and write are one system call and can return short), + :const:`1` means line buffered, any other positive value means use a buffer of + approximately that size. A negative bufsize (the default) means + the system default of io.DEFAULT_BUFFER_SIZE will be used. - .. note:: + .. versionchanged:: 3.2.4 - If you experience performance issues, it is recommended that you try to - enable buffering by setting *bufsize* to either -1 or a large enough - positive value (such as 4096). + *bufsize* now defaults to -1 to enable buffering by default to match the + behavior that most code expects. In 3.2.0 through 3.2.3 it incorrectly + defaulted to :const:`0` which was unbuffered and allowed short reads. + This was unintentional and did not match the behavior of Python 2 as + most code expected. The *executable* argument specifies a replacement program to execute. It is very seldom needed. When ``shell=False``, *executable* replaces the |