Update python generate_addresses to be more Pythonic

[Dr-Electron]

Description of change

This is just a cherry-pick of iotaledger/iota.rs#1651

Links to any relevant issues

Fixes #47

Type of change

• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How the change has been tested

The generated json was validated with the jsonschema generated by my tool

Change checklist

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have checked that new and existing unit tests pass locally with my changes