How to get an absolute file path in Python

>>> import os
>>> os.path.abspath("mydir/myfile.txt")
'C:/example/cwd/mydir/myfile.txt'

Also works if it is already an absolute path:

>>> import os
>>> os.path.abspath("C:/example/cwd/mydir/myfile.txt")
'C:/example/cwd/mydir/myfile.txt'

import os
os.path.abspath(os.path.expanduser(os.path.expandvars(PathNameString)))

Note that expanduser is necessary (on Unix) in case the given expression for the file (or directory) name and location may contain a leading ~/(the tilde refers to the user's home directory), and expandvars takes care of any other environment variables (like $HOME).

Install a third-party path module (found on PyPI), it wraps all the os.path functions and other related functions into methods on an object that can be used wherever strings are used:

>>> from path import path
>>> path('mydir/myfile.txt').abspath()
'C:\\example\\cwd\\mydir\\myfile.txt'

Update for Python 3.4+ pathlib that actually answers the question:

from pathlib import Path

relative = Path("mydir/myfile.txt")
absolute = relative.absolute()  # absolute is a Path object

If you only need a temporary string, keep in mind that you can use Path objects with all the relevant functions in os.path, including of course abspath:

from os.path import abspath

absolute = abspath(relative)  # absolute is a str object

This always gets the right filename of the current script, even when it is called from within another script. It is especially useful when using subprocess.

import sys,os

filename = sys.argv[0]

from there, you can get the script's full path with:

>>> os.path.abspath(filename)
'/foo/bar/script.py'

It also makes easier to navigate folders by just appending /.. as many times as you want to go 'up' in the directories' hierarchy.

To get the cwd:

>>> os.path.abspath(filename+"/..")
'/foo/bar'

For the parent path:

>>> os.path.abspath(filename+"/../..")
'/foo'

By combining "/.." with other filenames, you can access any file in the system.

You can use this to get absolute path of a specific file.

from pathlib import Path

fpath = Path('myfile.txt').absolute()

print(fpath)

Given a path such as mydir/myfile.txt, how do I find the file's absolute path relative to the current working directory in Python?

I would do it like this,

import os.path
os.path.join( os.getcwd(), 'mydir/myfile.txt' )

That returns '/home/ecarroll/mydir/myfile.txt'

In case someone is using python and linux and looking for full path to file:

>>> path=os.popen("readlink -f file").read()
>>> print path
abs/path/to/file