Simon Willison's Weblog: static-typing

Typing without having to type

2026-02-18T18:56:56+00:00

25+ years into my career as a programmer I think I may finally be coming around to preferring type hints or even strong typing. I resisted those in the past because they slowed down the rate at which I could iterate on code, especially in the REPL environments that were key to my productivity. But if a coding agent is doing all that typing for me, the benefits of explicitly defining all of those types are suddenly much more attractive.

Tags: programming, programming-languages, static-typing, ai-assisted-programming

Tests aren’t enough: Case study after adding type hints to urllib3

2021-10-18T19:03:38+00:00

Tests aren’t enough: Case study after adding type hints to urllib3

Very thorough write-up by Seth Michael Larson describing what it took for the urllib3 Python library to fully embrace mypy and optional typing and what they learned along the way.

Tags: python, static-typing, mypy, seth-michael-larson

Datasette unit tests: monkeytype_call_traces

2018-08-02T21:03:27+00:00

Datasette unit tests: monkeytype_call_traces

Faceted browse against every function call that occurs during the execution of Datasette’s test suite. I used Instagram’s MonkeyType tool to generate this, which can run Python code and generates a SQLite database of all of the traced calls. It’s intended to be used to automatically add mypy annotations to your code, but since it produces a SQLite database as a by-product I’ve started exploring the intermediary format using Datasette. Generating this was as easy as running “monkeytype run `which pytest`” in the Datasette root directory.

Via @simonw

Tags: python, sqlite, static-typing, testing, datasette, mypy

Pyre: Fast Type Checking for Python

2018-05-11T17:47:26+00:00

Pyre: Fast Type Checking for Python

Facebook’s alternative to mypy. “Pyre is designed to be highly parallel, optimizing for near-instant responses so that you get immediate feedback, even in a large codebase”. Like their Hack type checker for PHP, Pyre is implemented in OCaml.

Via Hacker News

Tags: facebook, python, static-typing, mypy, ocaml

How to Use Static Type Checking in Python 3.6

2018-04-19T18:30:37+00:00

How to Use Static Type Checking in Python 3.6

Useful introduction to optional static typing in Python 3.6, including how to use mypy, PyCharm and the Atom mypy plugin.

Via Gergely Szerovay

Tags: python, static-typing, mypy

Let your code type-hint itself: introducing open source MonkeyType

2017-12-15T02:22:30+00:00

Let your code type-hint itself: introducing open source MonkeyType

Instagram have open sourced their tool for automatically adding type annotations to your Python 3 code via runtime tracing. By default it logs the types it sees to a SQLite database, which means you can browse them with Datasette!

Tags: python, python3, static-typing

Why is Java perceived as not cool for startups? We seem to be getting a lot of feedback lately that a startup should be using Ruby on Rails, PHP, Python, etc., if they want to be agile and iterate quickly.

2010-11-14T12:21:00+00:00

My answer to Why is Java perceived as not cool for startups? We seem to be getting a lot of feedback lately that a startup should be using Ruby on Rails, PHP, Python, etc., if they want to be agile and iterate quickly. on Quora

I believe what takes the longest time in software engineering is not actually writing the code, but untangling it to find bugs, and Java is much more conducive to that, and the tooling is much stronger than for other languages.

You should re-evaluate your beliefs. Dynamic language programmers spend a great deal of time thinking about code quality and maintainability. TDD (and BDD), which I believe was first popularised within the Ruby community) are extremely widespread, and profiling and debugging tools are widely used and constantly improved. A strong test suite provides far more effective protection against bugs than static typing and an IDE.

Tags: java, programming, programming-languages, rails, startups, static-typing, quora, careers

Quoting Damien Katz

2008-06-11T06:51:21+00:00

Static typing in OO languages isn't the solution to software complexity, rather it's an enabler of it. Static typing is like giving a drunk a bunch of breath mints and saying "Don't drive drunk. But if you must, use these breath mints in case you get pulled over."

— Damien Katz

Tags: complexity, damien-katz, static-typing

Size Is The Enemy

2007-12-24T10:50:53+00:00

Size Is The Enemy

Jeff Atwood: “I’ve started a cottage industry mining Steve [Yegge]’s insanely great but I-hope-you-have-an-hour-to-kill writing and condensing it into its shorter form points.” Lots of verbose static typing apologists in the comments.

Tags: dynamic-languages, java, jeff-atwood, python, static-typing, steve-yegge

The Fishbowl: Type Inference and Java

2004-05-18T05:45:18+00:00

The Fishbowl: Type Inference and Java

Why Java’s implementation of static typing is stupid.

Tags: java, static-typing

ML Types Explained

2003-08-27T07:16:35+00:00

From a link on the mailing list edition of comp.lang.python, this talk on strong typing (in the form of heavily annotated slides) is an explanation of the ML type system and why it really doesn't suck. From the same thread, Felix is a new high level C++ style language with an ML style type system which looks like it could be worth experimenting with.

Tags: static-typing

Strong Typing vs Strong Testing

2003-05-04T20:32:56+00:00

In Strong Typing vs. Strong Testing, Bruce Eckel reconsiders the old idea that languages without strong typing can't be relied on to create large programs:

This became a puzzle to me: if strong static type checking is so important, why are people able to build big, complex Python programs (with much shorter time and effort than the strong static counterparts) without the disaster that I was so sure would ensue?

His conclusion is that type checking by the compiler does not garauntee the correctness of a program in the first place; it's just another test. Comprehensive unit testing can more than compensate for the lack of type checking in languages such as Python, especially since the huge productivity bonus provided by Python allows more tests to be written starting at an earlier stage in development.

Incidentally, Bruce recently added an RSS feed.

Tags: dynamic-languages, python, static-typing, bruce-eckel