[FIXED] Climbing the directory tree with Python

Issue

Let's say I have this folder structure:

My Project
├── One
│   ├── Another Thing
│   └── Two
│       ├── Three
│       │   └── foo.py
│       └── Whatever
└── Something Else

From foo.py, using Python 2, how would I get a list of all its parent directories? It should look something like this:

['My Project', 'One', 'Two', 'Three']

Solution

You can get the path of the current Python module by using the __file__ attribute set on all Python modules when Python loads them from a file on disk. This is a string representing the absolute or relative path (the latter usually only when it's the __main__ script) to the source file or .pyc byte-cache file of the module.

Use the os.path module to a) ensure that the path is absolute, and b), get all the directory names:

import os

HERE = os.path.dirname(os.path.abspath(__file__))

def path_list(pathname):
    drive, directory = os.path.splitdrive(pathname)
    path = [] if not drive else [drive]
    # with no UNC prefix, normpath guarantees the path uses os.sep
    path += filter(None, os.path.normpath(directory).split(os.sep))
    return path

The os.path.splitdrive() call is needed to on Windows, where network (UNC) paths can start with \\hostname\mount or with C:\\ (drive letters). The above includes such a prefix as the first element. Another happy side-effect of splitting of a UNC prefix is that this avoids one corner-case where os.path.normpath() would not replace os.altsep separators (/ on Windows) with \ (the Windows os.sep value) if the path starts with the special \\?\ or \\.\ prefixes.

Demo:

>>> __file__ = os.path.join(os.sep, 'My Project', 'One', 'Two', 'Three', 'foo.py')
>>> __file__
'/My Project/One/Two/Three/foo.py'
>>> HERE = os.path.dirname(os.path.abspath(__file__))
>>> HERE
'/My Project/One/Two/Three'
>>> path_list(HERE)
['My Project', 'One', 'Two', 'Three']

On Python 3.x, or if you are prepared to install a backport, you can also use the pathlib library; it provides Path instances that have a Path.parts attribute that gives you exactly the same info (with the root part represented by os.sep or the drive letter or UNC path on Windows):

try:
    from pathlib import Path
except ImportError:
    # pathlib2 backport
    from pathlib2 import Path

HERE = Path(__file__).resolve().parent
path_list = HERE.parts[1:] if HERE.root else HERE.parts

(Note: Path.parts produces a tuple, if you must have a list, pass the result to list() first).

You may also be interested in the Path.parents sequence, which gives you all the parent directories as Path instances, in reverse order:

>>> from pathlib import Path
>>> HERE = Path(__file__).resolve().parent
>>> HERE
PosixPath('/My Project/One/Two/Three')
>>> HERE.parts[1:] if HERE.root else HERE.parts
('My Project', 'One', 'Two', 'Three')
>>> list(HERE.parents)
[PosixPath('/My Project/One/Two'), PosixPath('/My Project/One'), PosixPath('/My Project'), PosixPath('/')]

Answered By - Martijn Pieters