[Python-Dev] Add os.path.resolve to simplify the use of os.readlink

[Christian Heimes]

Am 21.06.2012 14:55, schrieb Nick Coghlan:
> On Thu, Jun 21, 2012 at 9:26 PM, Christian Heimes <lists at cheimes.de> wrote:
>> BTW Is there a better way than raise OSError(errno.ELOOP,
>> os.strerror(errno.ELOOP), filename) to raise a correct OSError with
>> errno, errno message and filename? A classmethod like
>> "OSError.from_errno(errno, filename=None) -> proper subclass auf OSError
>> with sterror() set" would reduce the burden for developers. PEP mentions
>> the a similar idea at
>> http://www.python.org/dev/peps/pep-3151/#implementation but this was
>> never implemented.
> 
> According to the C code, it should be working at least for recognised
> errno values:
> 
> http://hg.python.org/cpython/file/009ac63759e9/Objects/exceptions.c#l890
> 
> I can't get it to trigger properly in my local build, though :(

Me neither with the one argument variant:

Python 3.3.0a4+ (default:c3616595dada+, Jun 19 2012, 23:12:25)
[GCC 4.6.3] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import errno
[73872 refs]
>>> type(OSError(errno.ENOENT))
<class 'OSError'>
[73877 refs]

It works work two arguments but it doesn't set strerror and filename
correctly:

>>> exc = OSError(errno.ENOENT, "filename")
[73948 refs]
>>> exc
FileNotFoundError(2, 'filename')
[73914 refs]
>>> exc.strerror
'filename'
[73914 refs]
>>> exc.filename
[73914 refs]

OSError doesn't accept keyword args:

>>> OSError(errno.ENOENT, filename="filename")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: OSError does not take keyword arguments


How about adding keyword support to OSError and derive the strerror from
errno if the second argument is not given?

Christian