To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

• The os and os.path modules.
• The __file__ constant
• os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
• os.path.dirname(path) (returns "the directory name of pathname path")
• os.getcwd() (returns "a string representing the current working directory")
• os.chdir(path) ("change the current working directory to path")

The special variable __file__ contains the path to the current file. From that we can get the directory using either pathlib or the os.path module.

Python 3

For the directory of the script being run:

import pathlib
pathlib.Path(__file__).parent.resolve()

For the current working directory:

import pathlib
pathlib.Path().resolve()

Python 2 and 3

For the directory of the script being run:

import os
os.path.dirname(os.path.abspath(__file__))

If you mean the current working directory:

import os
os.path.abspath(os.getcwd())

Note that before and after file is two underscores, not just one.

Also note that if you are running interactively or have loaded code from something other than a file (eg: a database or online resource), __file__ may not be set since there is no notion of "current file". The above answer assumes the most common scenario of running a python script that is in a file.

References

1. pathlib in the python documentation.
2. os.path - Python 2.7, os.path - Python 3
3. os.getcwd - Python 2.7, os.getcwd - Python 3
4. what does the __file__ variable mean/do?

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

is indeed the best you're going to get.

It's unusual to be executing a script with exec/execfile; normally you should be using the module infrastructure to load scripts. If you must use these methods, I suggest setting __file__ in the globals you pass to the script so it can read that filename.

There's no other way to get the filename in execed code: as you note, the CWD may be in a completely different place.