Python functions are objects

gistfile1.py

def shout(word="yes"):
    return word.capitalize()+"!"

print shout()
# outputs : 'Yes!'

# As an object, you can assign the function to a variable like any
# other object 

scream = shout

# Notice we don't use parenthesis: we are not calling the function, we are
# putting the function "shout" into the variable "scream". It means you can then
# call "shout" from "scream":

print scream()
# outputs : 'Yes!'

# More than that, it means you can remove the old name 'shout', the function will still
# be accessible from 'scream'

del shout
try:
    print shout()
except NameError, e:
    print e
    #outputs: "name 'shout' is not defined"

print scream()
# outputs: 'Yes!'