On Thursday, August 30, 2012 1:54:08 PM UTC+2, (unknown) wrote:
> Hello
>
>
>
> I'm slowly teaching myself python so apologies if this is a dumb question.
>
> but something has confused me with the os.stat() function:
>
>
>
> >>> s = os.stat(".")
>
> >>> print s
>
> posix.stat_result(st_mode=16877, st_ino=2278764L, st_dev=2053L, st_nlink=2,
> st_u
>
> id=1000, st_gid=100, st_size=4096L, st_atime=1346327745, st_mtime=1346327754,
> st
>
> _ctime=1346327754)
>
>
>
> What sort of object is posix.stat_result? Its not a dictionary or list or a
>
> class object as far as I can tell. Thanks for any help.
>
>
>
> B2003
Hi,
So let's try to figure this out. First of all, we can ask Python what object it
is.
>>> s = os.stat('.')
>>> type(s)
posix.stat_result
So it seems to be a custom type. However types can inherit from builtins like
list, tuple and dict, so maybe it still is a dict or a tuple. Let's ask Python
again:
>>> isinstance(s, dict)
False
>>> isinstance(s, (tuple, list))
False
Ok. So it is neither a list (tuple) nor a dict. So without reverting to the
source code, it is probably save to say that the result is a custom class where
the attributes can be accessed by the dot '.' notation. This is confirmed when
you do:
>>> dir(s)
......
'__setattr__',
'__sizeof__',
'__str__',
'__subclasshook__',
'n_fields',
'n_sequence_fields',
'n_unnamed_fields',
'st_atime',
'st_blksize',
'st_blocks',
'st_ctime',
'st_dev',
'st_gid',
'st_ino',
'st_mode',
'st_mtime',
'st_nlink',
'st_rdev',
'st_size',
'st_uid']
For example:
>>> print s.st_size
4096
In case of Linux I think that the result of os.stat(..) is a wrapping of a C
struct (a class with only attributes and no methods).
A small additional remark. Besides being a real dict or list (by means of
inheritance), custom class can also implement the interface (__getitem__ etc.).
If you want to know if an object implements this interface you could use the
types defined in the 'abc' and 'collections' standard modules. So instead of
checking if a type is a dict like this:
>>> isinstance(s, dict)
you could also check if it implements the dict interface:
>>> isinstance(s, collections.MutableMapping) # or similar
Regards,
Marco
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