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Writing Awesome Command-Line Programs in Python

Summary

Command-Line programs can have a lot to them - usually more than you think, yet often suffer from a lack of thought.

This is a tour through how to structure your code, tools in the standard library and some 3rd party libraries. Take your command-line programs to the next level!

Description

Python is a great language for writing command-line tools - which is why so much of Linux is secretly written in Python these days. Unfortunately, what starts as a simple script can quickly get out of hand as more features are added and more people start using it!

The talk will consist of a tour through various useful libraries and practical code showing how each can be used, and include advice on how to best structure simple and complex command-line tools.

Things to consider when writing command-line apps:

  • Single-file vs Multiple-file
  • Standard library only vs. 3rd party requirements
  • Installation - setup.py vs. native packaging

The different parts of a command-line program:

  • Option Parsing:
    • Libraries: getopt, optparse, argparse, docopt
    • Sub-commands
  • Configuration:
    • Formats: Ini file, JSON, YAML
    • Where should it be stored (cross-platform);
    • Having multiple configuration files, and allowing user config to override global config
  • Output:
    • Colour - colorama
    • Formatting output for the user
    • Formatting output for other programs
    • How do you know when your output is being piped to another program?
    • Managing logging and verbosity
  • Managing streamed input
  • Exit values: What are the conventions?
  • Interactive apps - REPL
  • Structuring a bunch of programs/commands around a shared codebase.
  • Command-line frameworks: clint, compago & cliff
  • Testing command-line apps
  • Writing command-line tools in Python 3 vs Python 2

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