How can I get the source code of a Python function?

Question

Suppose I have a Python function as defined below:

def foo(arg1,arg2):
    #do something with args
    a = arg1 + arg2
    return a

I can g

Answer 1

If you are using IPython, then you need to type "foo??"

In [19]: foo??
Signature: foo(arg1, arg2)
Source:
def foo(arg1,arg2):
    #do something with args
    a = arg1 + arg2
    return a

File:      ~/Desktop/
Type:      function