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Python
General-purpose language and its CPython interpreter.
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ModuleNotFoundError: No module named '…'
Python raises ModuleNotFoundError when the package is not installed for the interpreter that runs your code. Check sys.executable, then install with -m pip.
All Python error messages
python -m json.tool: pretty-print and validate JSON
Pretty-print or validate JSON from the shell with python -m json.tool (or python -m json on 3.14+). Sort keys, set indent, compact output and read JSON Lines.
All Python commands
Python 3.14 to 3.15: what changes and what breaks
Upgrading from Python 3.14 to 3.15: UTF-8 becomes the default encoding, lazy imports and frozendict arrive, and sqlite3, argparse and base64 change behaviour.
All Python version changes
Python version support and end-of-life dates
Which Python versions are supported in October 2026: 3.14 and 3.15 get bugfixes, 3.11 to 3.13 get security fixes only, 3.10 reached end of life on 2026-10-01.
All Python compatibility
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