Where is the math.py (socket.py, regex.py, etc.) source file? | Python

There are (at least) three kinds of modules in Python:
1. modules written in Python (.py);
2. modules written in C and dynamically loaded (.dll, .pyd, .so, .sl, etc);
3. modules written in C and linked with the interpreter; to get a list of these, type: import sys print sys.builtin_module_names