Python os.path.dirname returns unexpected path when changing directory

Question

Currently I do not understand, why pythons os.path.dirname behave like it does.

Let's assume I have the following script:

# Not part of the script, just for the current sample
__file__ = 'C:\\Python\\Test\\test.py'

Then I try to get the absolute path to the following directory: C:\\Python\\doc\\py

With this code:

base_path = os.path.dirname(os.path.dirname(os.path.realpath(__file__)) + '\\..\\doc\\py\\')

But why does the method os.path.dirname does not resolve the path, and print out (print (base_path):

C:\Python\Test\..\doc\py

I've expected the method to resolve the path to:

C:\Python\Test\doc\py

I just know this behaviour from the .NET Framework, that getting directory paths will always resolve the complete path and remove directory changes with ..\\. What do I have in Python for possibilities to do this?

Answer 1

Look into os.path.normpath

Normalize a pathname by collapsing redundant separators and up-level references so that A//B, A/B/, A/./B and A/foo/../B all become A/B. This string manipulation may change the meaning of a path that contains symbolic links. On Windows, it converts forward slashes to backward slashes.

The reason os.path.dirname works the way it does is because it's not very smart - it even work for URLs!

os.path.dirname("http://www.google.com/test")  # outputs http://www.google.com

It simply chops off anything after the last slash. It doesn't look at anything before the last slash, so it doesn't care if you have /../ in there somewhere.

Answer 2

os.path.normpath() will return a normalized path, with all references to the current or parent directory removed or replaced appropriately.