subprocess __exit__ attribute missing

[lambertdw]

BPO	13202
Nosy	@merwok

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2011-10-17.16:03:30.891>
created_at = <Date 2011-10-17.15:03:16.246>
labels = ['interpreter-core', 'invalid', 'library']
title = 'subprocess __exit__ attribute missing'
updated_at = <Date 2011-10-17.16:03:30.890>
user = 'https://bugs.python.org/LambertDW'

bugs.python.org fields:

activity = <Date 2011-10-17.16:03:30.890>
actor = 'eric.araujo'
assignee = 'none'
closed = True
closed_date = <Date 2011-10-17.16:03:30.891>
closer = 'eric.araujo'
components = ['Interpreter Core', 'Library (Lib)']
creation = <Date 2011-10-17.15:03:16.246>
creator = 'LambertDW'
dependencies = []
files = []
hgrepos = []
issue_num = 13202
keywords = []
message_count = 3.0
messages = ['145707', '145708', '145721']
nosy_count = 2.0
nosy_names = ['LambertDW', 'eric.araujo']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue13202'
versions = ['Python 2.7']

[lambertdw]

There are a number of issues with subprocess and __exit__ , 12494 status fixed among them.

Program (which doesn't work as I had hoped, but that's not the issue):

'file p.py'

import subprocess as S

with S.Popen(('cat','-n',),shell=False,stdin=S.PIPE,stdout=S.PIPE,bufsize=1,universal_newlines=True) as p:
p.stdin.write('these\n')
print(p.stdout.readline())

Use:

$ python3 p.py
�
Traceback (most recent call last):
  File "p.py", line 5, in <module>
    print(p.stdout.readline())
KeyboardInterrupt
$
$ python p.py
Traceback (most recent call last):
  File "p.py", line 3, in <module>
    with S.Popen(('cat','-n',),shell=False,stdin=S.PIPE,stdout=S.PIPE,bufsize=1,universal_newlines=True) as p:
AttributeError: __exit__
$
$ python
Python 2.7.1+ (r271:86832, Apr 11 2011, 18:13:53) 
[GCC 4.5.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>

[merwok]

Context management support was added in 3.2. It is not supported in 2.7.

[merwok]

To clarify: Python 2.5 and higher support the with statement syntax, but not all classes that could benefit from it have the __enter__ and __exit__ methods. So you don’t get a SyntaxError in Python 2.7 when you write “with Popen(...)”, but you get an AttributeError because Popen in 2.7 does not do its part to support context management. The built-in open function, on the contrary, supports with in 2.5 and higher.