Simon Willison's Weblog: trey-hunner

The features of Python's help() function

2025-03-03T19:15:30+00:00

The features of Python's help() function

I've only ever used Python's help() feature by passing references to modules, classes functions and objects to it. Trey Hunner just taught me that it accepts strings too - help("**") tells you about the ** operator, help("if") describes the if statement and help("topics") reveals even more options, including things like help("SPECIALATTRIBUTES") to learn about specific advanced topics.

Via @trey.io

Tags: python, trey-hunner

Python 3.13's best new features

2024-10-12T16:30:42+00:00

Python 3.13's best new features

Trey Hunner highlights some Python 3.13 usability improvements I had missed, mainly around the new REPL.

Pasting a block of code like a class or function that includes blank lines no longer breaks in the REPL - particularly useful if you frequently have LLMs write code for you to try out.

Hitting F2 in the REPL toggles "history mode" which gives you your Python code without the REPL's >>> and ... prefixes - great for copying code back out again.

Creating a virtual environment with python3.13 -m venv .venv now adds a .venv/.gitignore file containing * so you don't need to explicitly ignore that directory. I just checked and it looks like uv venv implements the same trick.

And my favourite:

Historically, any line in the Python debugger prompt that started with a PDB command would usually trigger the PDB command, instead of PDB interpreting the line as Python code. [...]

But now, if the command looks like Python code, pdb will run it as Python code!

Which means I can finally call list(iterable) in my pdb seesions, where previously I've had to use [i for i in iterable] instead.

(Tip from Trey: !list(iterable) and [*iterable] are good alternatives for pre-Python 3.13.)

Trey's post is also available as a YouTube video.

Via @treyhunner

Tags: python, trey-hunner

Every dunder method in Python

2024-03-20T03:45:58+00:00

Every dunder method in Python

Trey Hunner: "Python includes 103 'normal' dunder methods, 12 library-specific dunder methods, and at least 52 other dunder attributes of various types."

This cheat sheet doubles as a tour of many of the more obscure corners of the Python language and standard library.

I did not know that Python has over 100 dunder methods now! Quite a few of these were new to me, like __class_getitem__ which can be used to implement type annotations such as list[int].

Tags: python, trey-hunner