Python function decorators are great at retaining state information for use during the function call

tracer.py

#!/usr/bin/env python

# Function decorators are great at retaining state information for use
#   during the function call

class tracer:
    def __init__(self, func):
        self.calls = 0
        self.func = func
    def __call__(self, *args, **kwargs):
        self.calls += 1
        print('call {} to {}'.format(self.calls, self.func.__name__))
        return self.func(*args, **kwargs)


@tracer
def spam(a, b, c):
    print(a + b + c)

@tracer
def ham(d, e, f):
    print(d + e + f)

spam(1, 2, 3)
ham('orange', 'purple', 'mauve')

spam(4,5,6)
ham('yes ', 'no ', 'maybe')

## RETURNS:
>>> call 1 to spam
>>> 6
>>> call 1 to ham
>>> orangepurplemauve
>>> call 2 to spam
>>> 15
>>> call 2 to ham
>>> yes no maybe

Closely based on material in Lutz Learning Python Chapter 39: Decorators