[Python-3000] A few small py3k wishes

[Thomas Wouters]

On 4/3/06, Talin <talin at acm.org> wrote:
>
> Thomas Wouters <thomas <at> python.org> writes:
>
> > I'm not sure what you're missing. The __main__ module has __file__:
>
> Except that they are not the same!
>
> When I print __file__ from my __main__ module, I get the name of the
> file only, no path.


You get the path that was used to run the file:

centurion:~ > python ~thomas/tmp.py
__file__: /home/thomas/tmp.py
__main__.__file__: /home/thomas/tmp.py


> However, when I print __file__ from my imported module, I get the
> complete, absolute path to the module.


Incorrect: you get the path that was used to import the module. If a
relative path is in sys.path (like its first element usually is), the
module's __file__ will be a relative path:

 centurion:~ > python -c 'import tmp'
__file__: tmp.py

In fact, if I do a "print dir()" for the main module and the imported
> module, I get something like this:
>
> main: ['__builtins__', '__file__', '__name__', '__pymate', 'input',
> 'raw_input']
> imported: ['__builtins__', '__doc__', '__file__', '__name__',
>                  '__path__', 'fnmatch', 'os']
>
> Note that the impored module has a "__path__" attribute, while the
> main module does not.


Only packages have a __path__ attribute. Try checking on a module that is a
.py file. Likewise, not all modules have a __file__ attribute:

>>> posix.__file__
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
AttributeError: 'module' object has no attribute '__file__'

The reason I bring this up is that it is a common usage pattern for
> a particular source file to be run as both a main and as an imported
> module. Suppose you have a bunch of test data that is in a subdir
> of your source file. You'd like to be able to have a single, uniform
> way to locate your module's data, regardless if you are __main__
> or not.


__file__ is it. os.path.abspath() it with os.getcwd().

--
Thomas Wouters <thomas at python.org>

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