Why does os.path use both '\' and '/'?

Question

When I get the os.path.dirname() of a file on Windows, it uses the / character (gets converted to \\ by Windows), but then when I os.path.join() that path with other things, it uses the \\ character (as expected).

import os

cwd = os.path.dirname(__file__)
print(cwd)                            # C:/Users/me/Documents/dir1
parent_dir = os.path.join(cwd, '..')
print(parent_dir)                     # C:/Users/me/Documents/dir1\..

Windows handles this just fine. As per MSDN :

File I/O functions in the Windows API convert "/" to "\\" as part of converting the name to an NT-style name, except when using the "\\\\?\\" prefix as detailed in the following sections.

But why does the use of both slashes occuring in the first place?

EDITS:

I run the command using python myfile.py from Cygwin shell.

I am using the Anaconda3 distribution, which is installed at C:\\Users\\me\\AppData\\Local\\Continuum\\Anaconda3\\python.exe .

λ which python
/cygdrive/c/Users/me/AppData/Local/Continuum/Anaconda3/python

Answer 1

Since you're running from cygwin, the paths are not native, but altered for cygwin to be able to work properly (MSYS does the same).

So as a side effect, when python asks for current file, it is returned with slashes.

BUT anaconda is still a native windows distribution, which explains that you get \\ (native os.sep ) when joining strings.

To get __file__ path with native separators ( \\ here), just do:

os.path.normpath(__file__)