New submission from Nick Coghlan <[email protected]>:
Currently, pipes in the subprocess module work strictly with bytes I/O,
*unless* you set "universal newlines=True". In that case, it assumes an output
encoding of UTF-8 for stdout and stderr and applies universal newlines process.
When stdin/out/err are remapped to ordinary I/O streams then 'encoding' and
'errors' can be specified as usual, but it is currently challenging to do this
for pipes. Since they're created internally by the subprocess module, user code
doesn't get the opportunity to wrap them when using the convenience APIs. When
using Popen objects, you have to create the object, then wrap each stream
individually (rebinding the attributes as you go).
My suggestion is that we add a new option for the stdin/out/err arguments:
class TextPipe:
def __init__(self, encoding, errors='strict'):
self.encoding = encoding
self.errors = errors
So to read UTF-8 encoded data from a subprocess, you could just do:
data = check_stdout(cmd, stdout=TextPipe('utf-8'), stderr=STDOUT)
There are at least a couple of other alternatives here:
- separate out the pipe creation logic from the Popen logic so it is possible
to create and wrap the pipe objects explicitly and then pass the wrapped pipe
object to the subprocess invocation APIs. 'TextPipe' would then actually be
such a wrapped pipe, rather than merely instructions to tell Popen what kind of
pipe to create.
- instead of adding 'TextPipe', just re-use the PIPE name (with the class
itself still being used as a marker constant to request implicit creation of a
binary PIPE)
----------
assignee: docs@python
components: Documentation
messages: 148022
nosy: docs@python, ncoghlan
priority: normal
severity: normal
stage: needs patch
status: open
title: Better support for pipe I/O encoding in subprocess
versions: Python 3.3
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Python tracker <[email protected]>
<http://bugs.python.org/issue13442>
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