how python dir works

[cheung]

how does the function  "dir" works, where can I get the python-c  source of dir in py2.7 project.

I looked the python_c source for hours, can't find how dir works. 

for example:
   if a user input a *.py source file like foo.py, i wanna parse the file, and find all the functions and all the classes in the foo.py.

i wanna use the python-c source or python Lan. to solve this problem, I've tried to view the python-c project, and ask google for help, but doesn't work.

can anyone help me?