How to get symlink target in Python?

Question

Using Python, I need to check whether hundreds of symlinks are correct and recreate them when not. What I do now is to compare real paths of what I want and what I have, but it's slow because it's over NFS with an automount.

Otherwise I'm going to run a subprocess with the command 'ls -l' and work on the list of strings returned. I would prefer a better solution, using a Python library...

Edit1: I have: link_name -> link_target and then link_target -> a_real_file. What I need is to extract link_target from link_name, not a_real_file. I don't care if the real file does not exist.

Edit2: Maybe I did not express correctly. What I mean by a correct symlink is 'a link that point to a predefined path, even if it does not exist'. So I need to check that:

link_name_1 -> target_1
link_name_2 -> target_2

That's why I need to extract targets, not the real paths. Then I compare them to a reference (dictionary). So my question is: How do I extract the target path?

Answer 1

The problem with os.readlink() is it will only resolve 1 step of the link. We can have a situation where A links to another link B, and B link is dangling.

$ ln -s /tmp/example/notexist /tmp/example/B
$ ln -s /tmp/example/B /tmp/example/A
$ ls -l /tmp/example
A -> /tmp/example/B
B -> /tmp/example/notexist

Now in Python, os.readlink gives you the first target.

>>> import os
>>> os.readlink('A')
'/tmp/example/B'

But in most situations I assume we are interested in the resolved path. So pathlib can help here:

>>> from pathlib import Path
>>> Path('A').resolve()
PosixPath('/tmp/example/notexist')

For older Python versions:

>>> os.path.realpath('A')
'/tmp/example/notexist'