How can I prevent Python 3.13 REPL from auto-indenting pasted code?

The behavior you’re seeing is due to the REPL’s auto‐indent “smart paste” feature. When you paste code that contains a block (e.g. after an if statement with a colon), the REPL automatically indents every new line relative to the first. This can cause extra spaces to be inserted when the pasted code wasn’t originally written in a way that fits the REPL’s expectations.

Here are a few ways to work around this:

1. Use a Paste Mode Feature
   If you use IPython instead of the standard Python REPL, you can invoke paste mode with one of its commands:

   • %paste: This command takes the code from your clipboard and executes it as a single block.
   • %cpaste: Similar to %paste but lets you manually end the pasted block by typing --.

   Example in IPython:

   PYTHONCopied
   In [1]: %cpaste
   Pasting code; enter '--' alone on the line to finish.
   :if revenue_growth_Q1 > 0:
   :        RevG1="U"
   :else:
   :        RevG1="D"
   :--

   These commands bypass much of the REPL’s auto-indenting.

2. Run the Code from a File
   Rather than pasting into the REPL, save your code in a file (say, script.py) and run it. This avoids the interactive shell’s autoindent behavior entirely:

   BASHCopied
   python script.py

3. Manually Adjust Paste Behavior
   In the standard CPython REPL, there isn’t a built-in paste mode. One hack is to change the secondary prompt (sys.ps2), but that won’t fully prevent the interpreter from autoindenting lines after a block header. For example:

   PYTHONCopied
   >>> import sys
   >>> sys.ps2 = ''

   However, this isn’t a robust solution and might lead to other usability issues.

The cleanest solutions are to either use IPython with its dedicated paste commands or to run your code from a file. This way, you won’t need to manually delete extra spaces.