Roll to get the ultimate answer of life, universe, and everything.

retry_decorator.py

import time
import math
import random
import sys

# Retry decorator with exponential backoff
def retry(tries, delay=3, backoff=2):
    '''Retries a function or method until it returns True.
    
    delay sets the initial delay in seconds, and backoff sets the factor by which
    the delay should lengthen after each failure. backoff must be greater than 1,
    or else it isn't really a backoff. tries must be at least 0, and delay
    greater than 0.'''
    
    if backoff <= 1:
        raise ValueError("backoff must be greater than 1")
    
    tries = math.floor(tries)
    if tries < 0:
        raise ValueError("tries must be 0 or greater")
    
    if delay <= 0:
        raise ValueError("delay must be greater than 0")
    
    def deco_retry(f):
        def f_retry(*args, **kwargs):
            mtries, mdelay = tries, delay # make mutable
            
            rv = f(*args, **kwargs) # first attempt
            while mtries > 0:
                if rv is True: # Done on success
                    return True
                
                mtries -= 1      # consume an attempt
                for i in range(mdelay):
                    time.sleep(1)
                    sys.stdout.write('.')
                    sys.stdout.flush()
                print ""
                time.sleep(mdelay) # wait...
                mdelay += backoff  # make future wait longer
                
                rv = f(*args, **kwargs) # Try again
                
            return False # Ran out of tries :-(
            
        return f_retry # true decorator -> decorated function
    return deco_retry  # @retry(arg[, ...]) -> true decorator


@retry(15, 3, 2)
def roll_the_ultimate_answer():
    if random.randint(1, 100) == 42:
        print "Congratulations, you got the answer!"
        print "42"
        return True
    else:
        print "bang!"

print roll_the_ultimate_answer()