[issue15228] os.utime() docs not clear on behavior on nonexistant files

[Daniel Grace]

New submission from Daniel Grace :

The documentation for os.utime() at 
http://docs.python.org/py3k/library/os.html#os.utime states:

"Set the access and modified times of the file specified by path. [...] The 
effect is similar to running the Unix program touch on the path.)"

Unlike 'touch', os.utime() will not create an empty file if called on a file 
that does not exist.  IMO the current behavior is correct, but the comparison 
of os.utime() to touch implies that it would create empty files.

I suggest clarifying the documentation to emphasize that os.utime() will not 
create new files and raises OSError in the event that the file does not exist.

--
assignee: docs@python
components: Documentation
messages: 164422
nosy: dewin, docs@python
priority: normal
severity: normal
status: open
title: os.utime() docs not clear on behavior on nonexistant files
type: enhancement

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[issue20149] 'with instance' references class's __enter__ attribute rather than instance's

[Daniel Grace]

New submission from Daniel Grace:

I was writing code for a class that uses one threading.RLock per object.  For 
convenience, I wanted to be able to use that lock's context manager and 
acquire/release methods without referencing the lock directly, so I opted to 
take a shortcut by assigning self.__enter__ = self.lock.__enter__ and so forth.

This fails in Python 3.3.1 (self-compiled on Debian) and both "3.3.2+" and 
"2.7.5+" (currently available Ubuntu packages).  Judging by the error messages, 
it looks 'with' is examining the __enter__ and __exit__ attributes defined on 
the instance's class, rather than those defined on the instance itself.

The workaround here is simple enough, but I'm under the impression that it 
shouldn't be needed anyways.

Test case follows:

import threading

class Foo(object):
#   Uncommenting these yields "NoneType is not callable" rather than an 
AttributeError
#   __enter__ = None
#   __exit__ = None
#   acquire = None
#   release = None
#   lock = None

def __init__(self):
self.lock = threading.RLock()
print(repr(self.lock))
self.__enter__ = self.lock.__enter__
self.__exit__ = self.lock.__exit__
self.acquire = self.lock.acquire
self.release = self.lock.release

foo = Foo()
# These all function as expected.  The fourth line fails (correctly) on 2.7.5.
print(repr(foo.__enter__))
print(repr(foo.__exit__))
print(foo.__enter__())
print(foo.__exit__())

# This does not
with foo:
pass

--
components: Interpreter Core
messages: 207457
nosy: dewin
priority: normal
severity: normal
status: open
title: 'with instance' references class's __enter__ attribute rather than 
instance's
type: behavior
versions: Python 2.7, Python 3.3

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