About these Python error pages

This site explains Python error messages one at a time, in the words the interpreter uses, so that the message you paste into a search box finds the page about it.

How every page is checked

Each page is a short file with the example code in it. A script writes that code into an empty folder and runs it on every interpreter this site covers: CPython 3.9.6, 3.10.22, 3.11.17, 3.12.15, 3.13.17, 3.14.9 and 3.15.1. What each one prints goes onto the page as it came out, so the tables of wordings are output, not memory. A page whose example stops failing, or fails with a different message than the page names, does not build.

The 3.9 runs use the Python that Apple ships with its command line tools; the others are the standalone builds uv installs. The examples were last run on October 25, 2026.

Explanations and fixes are checked against the Python documentation, the PEPs and the packaging specifications, which each page lists under Sources with the date they were read.

The name

It is what people say at a traceback. The pages themselves stay calm: what the message means, why it happened, what to change.

Who runs it

An independent site, not affiliated with the Python Software Foundation or the CPython project. “Python” and the Python logos are trademarks of the PSF; this site uses neither logo.