Episode #28: The meaning of _ in Python

Published Fri, Jun 2, 2017, recorded Wed, May 31, 2017.

Brian #1: pep8.org : PEP 8 — the Style Guide for Python Code

  • "This stylized presentation of the well-established PEP 8 was created by Kenneth Reitz (for humans)."
  • From PEP 8: "This document gives coding conventions for the Python code comprising the standard library in the main Python distribution."
  • PEP8 is not only used for the standard library. Many if not most open source Python packages adhere to at least most of the PEP8 recommendations
  • testing plugins can help you make sure your code meets the guidelines (for good or bad).
  • The pep8.org presentation is easy to read, with a left side clickable table of contents.
  • Nice color coded examples. Green for good, Red for bad.
  • links to specific items make it easy to share with others something specific.
  • Good advice, but don't be a pep8-bully.

Michael #2: Tokio: Asyncio event loop written in Rust language

  • Asyncio event loop written in Rust language
  • It is still in alpha stage.
  • It provides most of asyncio event loop apis, except udp.
  • TCP api is more or less stable
  • Aiohttp tests pass with tokio loop (~1800 tests)
  • Mostly interesting as an example of Rust + Python
  • Project is still in early stage of development

Brian #3: Python Boilerplate

  • Interactive online tool for creating script and small project boilerplate code.
  • Just starting, with "how to help" link.
  • Select
    • Python 2 or 3
    • executable script or not
    • argparse
    • logging
    • .gitignore
    • Flask
    • unittest or pytest
    • tox
  • fills in main.py, plus other files like test_sample.py, requirements.txt, tox.ini, etc.

Michael #4: Instagram switching to Python 3 on one branch

  • Ancient Django but still productive
  • Ran out of 32-bit user IDs before they ran out of Django power.
  • Added sharing support to Django Orem
  • Turned off GC for perf
  • Upgraded entirely to 3.6 in a few months
  • Why?
    • Type hints
    • Scaling server perf
    • asyncio
  • Python 3 is where the future community work is happening
  • Strategies
    • No user impact
    • Still shipping
    • Testing process was interesting
  • This is a concrete roadmap for every large company

Brian #5: The Meaning of Underscores in Python

  • single and double underscore meanings
  • dunder is "double underscore"
    • Single Leading Underscore: _var
  • method or variable for internal use
  • convention only
  • doesn't apply to collection.namedtuple
    • Single Trailing Underscore: var_
  • used to avoid name collision with keywords
    • Double Leading Underscore: __var
  • internal use by a single class level.
  • Python will name mangle this so that subclasses don't have to avoid parent class double leading underscore names
    • Double Leading and Trailing Underscore: __var__
  • no name mangling
  • special names. dunder methods
  • __call__ and __init__, etc.
    • Single Underscore: _
  • in code : temp variable, don't care variable
  • won't get a warning if you don't reference it again
  • in REPL: last value

Michael #6: The future is looking bright for Python

  • Stack Overflow recently released a cool new tool called Trends (previously covered)
  • Check out the Most Popular Languages trend chart
  • Python has, by a very large margin, the greatest positive slope (future?)
  • And Py3 vs Py2

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