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On 4/21/2012 8:53 PM, Brett Cannon wrote:

imp.cache\_from\_source() (and thus also imp.source\_from\_cache()) has special semantics compared to how os.path.join() works. For instance, if you look at test\_imp you will notice it tries to use the same path separator as is the farthest right in the path it is given::

self.assertEqual(imp.cache\_from\_source('\\\\foo\\\\bar/baz/qux.py', True), '\\\\foo\\\\bar\\\\baz/\_\_pycache\_\_/qux.{}.pyc'.format(self.tag))

But if you do the same basic operation using ntpath, you will notice it simply doesn't care::

>>> ntpath.join(ntpath.split('a\\\\b/c/d.py')\[0\], '\_\_pycache\_\_', 'd.cpython-32.pyc')

'a\\\\b/c\\\\\_\_pycache\_\_\\\\d.cpython-32.pyc

Basically imp.cache\_from\_source() goes to a bunch of effort to reuse the farthest right separator when there is an alternative separator \*before\* and path splitting is done. But if you look at ntpath.join(), it doesn't even attempt that much effort.

Now that we can reuse os.path.join() (directly for source\_from\_cache(), indirectly through easy algorithmic copying in cache\_from\_source()) do we want to keep the "special" semantics, or can I change it to match what ntpath would do when there can be more than one path separator on an OS (i.e. not do anything special)?

Is there an issue here with importing from zip files, which use / separator, versus importing from the file system, which on Windows can use either / or \\ ? I don't know if imp.cache\_from\_source cares or is aware, but it is the only thing I can think of that might have an impact on such semantics. (Well, the other is command line usage, but I don't think you are dealing with command lines at that point.)