Answer 1

You can start with studying and analysing the existing pentest tools available on for free online.
Check out how they are created? What are the logics and parameters considered? etc..
There are many open source pentest tools written in python. Below I have listed some.
Most of the listed tools are written in Python, others are just Python bindings for existing C libraries, i.e. they make those libraries easily usable from Python programs.
-Scapy
-pypcap
-Pycapy
-pylibpcap
-pynids
-Pytbull
-Paimei
-mono.py
-pyEMU
-fuzzer.py
-Windmill
-pydasm
etc.