future-fstrings.md

customizing python's syntax with terrible hacks

abstract

What if macros, new syntax, and more were just a pip install away?

In this talk I'll show how a load-bearing comment and an obscure python import system feature make this a reality!

We'll dive into each of these features and how they can be chained together to enable custom source pre-processing.

I'll demo how I used these techniques to make f-strings work in python 2, added support for dictionary unpacking in python, and more!

supplemental information

30 minute talk ideally

notes / outline: https://github.com/anthonywritescode/cfp/blob/main/future-fstrings.md

• project: https://github.com/asottile/future-fstrings
• project: https://github.com/asottile/dict-unpacking-at-home

previous presentations:

• python now has dict unpacking? https://youtu.be/eqiM0xRmFJg
• what is a .pth file? https://youtu.be/mzxQrgvuRFg
• code samples: https://github.com/anthonywritescode/explains

outline

intro (~5 minutes)

• who am I?
• y tho? (it started out as a joke how did it end up like this?)

the meat of the presentation (~25 minutes)

• python 2 f-strings demo (~2 minutes)
• basic explanation of encodings (utf-8 to turn bytes into text) (3 minutes)
• registering custom encodings in python (1 minute)
• ok registering custom encodings requires code -- how to automate it?
• .pth files: special import system magic (5 minutes)
• packaging a .pth file (3 minutes)
• putting that together: a custom encoding which performs source manipulation! (10 minutes)
  • parse / unparse token stream (tokenize-rt)