xmpl.py

# define our higher-order function
def more_verboser(func):
    def inner(x):
        val = func(x)
        print val
        return val
        
    return inner

# defined without decorator
def double(x):
    return x * 2
    
double = more_verboser(double)


# so now calling double(2) would print "4" to the console, but the syntax is a
# little silly - it's confusing to have obj(other_call)? what? So we do
# things a little differently, as a matter of convention:
@more_verboser
def double(x):
    return x * 2

# this is EXACTLY the same call as the line starting with `double = ...`,
# except it's a nicer SYNTAX. Again, it's purely a syntactical change, so we
# call these kind of things "Syntactic Sugar", since it makes the syntax
# "sweeter".

# This gets even better, since we can put multiple "decorators" on a single
# function, which would be really confusing if we had to wrap them manually.
@more_verboser
@more_verboser
def double(x):
    return x * 2
    
# so calling that will print the result twice, since the inner functions get
# evaluated twice