What is pycache?

__pycache__ is a directory that is created by the Python interpreter when it imports a module. It contains the compiled bytecode of the module, which can be used to speed up subsequent imports of the same module. The bytecode is specific to the version of Python that was used to generate it, so different versions of Python will create different bytecode files.

Here is a code snippet that demonstrates how __pycache__ is created:

How pycache is created in Python

import my_module
# The first time this is run, the interpreter will import my_module, and create a __pycache__ directory
# in the same directory as my_module.py

import my_module
# The second time this is run, the interpreter will look for a compiled version of my_module in the 
# __pycache__ directory, and use that instead of re-compiling the source code.

You can verify the directory and its contents using a shell command:

ls -la __pycache__/
# Output typically shows .pyc files like my_module.cpython-311.pyc

It's worth noting that __pycache__ is created by default in Python 3.2+ during normal execution. To prevent the interpreter from writing bytecode files, you can run Python with the -B flag or set the PYTHONDONTWRITEBYTECODE environment variable. You can safely delete __pycache__ directories at any time; the interpreter will simply regenerate them on the next import.