Question

Let’s say you have functions a and b. Can you, by calling function a, replace function b with another function?

I know you can do b=a(b), but can you change b with just doing a(b)?

Answer 1

Functions and methods are attributes of modules and classes respectively. So you can modify the required attribute to point to another function.

>>> __name__
'__main__'
>>> def a():
...     print 'a'
... 
>>> def b():
...     print 'b'
... 
>>> import sys
>>> sys.modules['__main__'].b = a
>>> b()
a

For a class:

>>> class A(object):
...     def a(self):
...             print 'a'
...     def b(self):
...             print 'b'
... 
>>> A.b = A.a
>>> x = A()
>>> x.b()
a

And if you have a variable holding the name to replace, then use setattr, for example:

setattr(sys.modules['__main__'],'b',a)
setattr(A,'b',A.a)

Just replace the string (‘b’) with your variable.

Not sure why you would want to though? It will make for confusing code.