What causes "ModuleNotFoundError: No module named 'readline'"?

Running a Linux/Mac Python script on a Windows machine An AI tool (like Ollama or LocalAI wrappers) assuming a Unix environment

Error2 Fixes Available

ModuleNotFoundError: No module named 'readline'

ModuleNotFoundError: No module named 'readline'

What does this error mean?

The `readline` module provides text-completion and history capabilities for Python's interactive prompts. However, `readline` is a Unix/Linux-only C library and does not exist on Windows. When you try to run a script containing `import readline` on Windows, it crashes.

Common Causes

Running a Linux/Mac Python script on a Windows machine
An AI tool (like Ollama or LocalAI wrappers) assuming a Unix environment

How to Fix It (2 Solutions)

Install the Windows alternative (pyreadline3)

On Windows, you can install `pyreadline3`, which acts as a drop-in polyfill replacement for `readline`.

Code

pip install pyreadline3

Conditionally import readline in Code

If you are the developer writing the script, use a try/except block to gracefully degrade or load the alternative.

Code

try:
    import readline
except ImportError:
    try:
        import pyreadline3 as readline
    except ImportError:
        pass # Optional: prompt user to install pyreadline3

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