Try something a predefined number of times

try.py

#!/usr/bin/env python
"""
Example Python pattern: try something a number of times, and only really fail
after that.
"""


import sys
import time


NUM_FAILS = int(sys.argv[1])
NUM_TRIES = int(sys.argv[2])
RETRY_SLEEP = 1


def some_computation(i):
    if i < NUM_FAILS:
        raise Exception('Computation failed')
    return i


result = None

for i in range(NUM_TRIES - 1):
    try:
        result = some_computation(i)
        break
    except Exception:
        time.sleep(RETRY_SLEEP)
else:
    try:
        result = some_computation(NUM_TRIES)
    except Exception as e:
        print e
        sys.exit(1)

print 'The result is %d' % result