os.path.dirname and os.path.join

First, let's understand what each function do:

os.path.abspath(path)

Return a normalized absolutized version of the pathname path.

You used:

os.path.abspath(sys.argv[0]) 

Example:

>>> print(os.path.abspath(sys.argv[0])) /usr/bin/ipython 

Pathlib equivalent:

>>> pathlib.Path(sys.argv[0]).resolve() /usr/bin/ipython 

os.path.dirname(path)

Returns the directory name of path.

You used:

os.path.dirname(os.path.abspath(sys.argv[0])) 

Example:

>>> os.path.dirname('/usr/bin/ipython') /usr/bin 

Pathlib equivalent:

import pathlib path = pathlib.Path(sys.argv[0]) modpath = path.parent 

os.path.join(path1, path2, ...)

Joins one or more path components.

You used:

os.path.join(modpath, '../../datas/orcl-1995-2014.txt') 

Example:

>>> print(os.path.join('/etc', 'dir1', '..', 'dir2', 'dir3/dir4')) /etc/dir1/../dir2/dir3/dir4 

Pathlib equivalent:

datapath = modpath.parent.parent / 'datas' / 'orcl-1995-2014.txt' 

Now, let's follow the code:

1. Resolve sys.argv[0] - Which is the path to your Python script. Let's say it is /usr/bin/python.
2. Apply os.path.abspath on /usr/bin/python - You can try it in the interpreter. The result is /usr/bin/python, since it is already an absolute path.
3. Apply os.path.dirname on the result (/usr/bin/python). The result is the directory name of usr/bin/python', which is/usr/bin. Save it inmodpath`.
4. Concatenate modpath (/usr/bin/) with ../../datas/orcl-1995-2014.txt using os.path.join - which results in /usr/bin/../../datas/orcl-1995-2014.txt. Save it on datapath.

os.path.abspath(sys.argv[0]) would return the absolute path. os.path.dirname(path) function returns the head of the path.

modpath would be the head of path.

os.path.join(path1, path2) function would join two directory paths.

Hope this helps!