Why Does Pasting Code in Windows Terminal Cause Indentation Errors in Python 3.13.1?

Below is an explanation of what’s happening and some workarounds.

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What’s Going On

With Python 3.13.1, a change in the interactive REPL (used when you run Python in the Windows terminal) now causes pasted code to be interpreted differently. When you right-click paste an indented code block into the Windows terminal, the REPL in 3.13.1 can misinterpret the whitespace—often because extra or unexpected newline characters are inserted—which leads to “unexpected indent” errors. This behavior did not occur in 3.12.x because of subtle differences in how input from the terminal was processed.

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Workarounds

1. Use an External Editor or a Script File
   Instead of pasting directly into the interactive prompt, paste your code into a file (e.g., script.py) and run it with:

   BASHCopied
   python script.py

2. Switch Paste Methods
   Some users report that using keyboard shortcuts (like Shift+Insert) rather than the default right-click paste in Windows terminal helps reduce the issue.

3. Enable Paste Mode (if available)
   Some interactive shells have a “paste mode” which delays evaluating pasted code until you signal it’s complete (similar to how Vim’s paste mode works). Although Python’s REPL doesn’t natively support this out of the box, you might look into terminal configurations or tools that simulate such behavior.

4. Downgrade Python
   If pasting code into the REPL is essential for your workflow, consider continuing with Python 3.12.x until the issue is addressed in a later Python 3.13 patch release.

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Summary

This indentation error when pasting code into the Windows terminal using Python 3.13.1 is a known issue resulting from changes in the REPL’s handling of multi-line input. You can work around it by using an editor to run your code, trying a different paste method, or downgrading to Python 3.12.x until a fix is released in a later version.

If you have further technical questions on this subject, feel free to ask!