How do you read the source code of a Python module?

Question

I'm trying to understand how some built-in Python modules work under the hood.

For example, with the code:

from Tkinter import *
root = Tk()
root.mainloop()

Where is the definition of the function Tk?

I've been searching through the tkinter source code but cannot find it. The code several time calls import Tkinter which is also strange because this is Tkinter, so why is it importing itself?

Hope someone can help resolve my confusion

Answer 1

class Tk is in:

• Py 2.7: Tkinter.py
• Py 3.6: __init__.py.

In general, when you import Foo, if Foo is a module implemented using Python code, and there is a Foo/__init__.py in Python's search path, that file runs. Some more information here, plus official docs on modules for Python 2 or Python 3. That may not be the case for modules built in to the Python interpreter, such as 2.7's Tkinter.

Tkinter specifics

• In Python 2, Tkinter is a Python module and tkinter (lowercase) is a C module that Tkinter uses (source).
• In Python 3, tkinter (lowercase) is a Python module and _tkinter (with underscore) is the C module that tkinter uses (source).