using ptags.py for tag file

1. Place the ptags.py file in your $PATH.
2. From the project directory containing your Python project, run the following command:

find . -name "*.py" -print | xargs ptags.py

I was previously using various inefficient methods to achieve this. The ptags.py script is similar to Ctags ctags is a shell command that generates an index (tag) file of programmatic identifiers parsed from source code files of various programming languages to aid with code comprehension. The tags are often used by a source-code editor to lookup the definition of an identifier while the user develops the source code. Alternatively, the command supports an output format that is a human-readable cross reference. but specifically designed for Python code.