In Python, the term monkey patch refers to dynamic (or run-time) modifications of a class or module. In Python, we can actually change the behavior of code at run-time.

monk.py

class A:
def func(self):
print "func() is being called"

We use above module (monk) in below code and change behavior of func() at run-time by assigning different value.

import monk
def monkey_f(self):
print "monkey_f() is being called"

replacing address of "func" with "monkey_f"

monk.A.func = monkey_f
obj = monk.A()

calling function "func" whose address got replaced

with function "monkey_f()"

obj.func()

Output :monkey_f() is being called