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...?
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.