Finding the source code for built-in Python functions?

python python-internals
user1073865 picture user1073865 · Dec 22, 2011 · Viewed 114.7k times · Source

Is there a way to see how built in functions work in python? I don't mean just how to use them, but also how were they built, what is the code behind sorted or enumerate etc...?

Answer

Chris picture Chris · Dec 22, 2011

Since Python is open source you can read the source code.

To find out what file a particular module or function is implemented in you can usually print the __file__ attribute. Alternatively, you may use the inspect module, see the section Retrieving Source Code in the documentation of inspect.

For built-in classes and methods this is not so straightforward since inspect.getfile and inspect.getsource will return a type error stating that the object is built-in. However, many of the built-in types can be found in the Objects sub-directory of the Python source trunk. For example, see here for the implementation of the enumerate class or here for the implementation of the list type.

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