retry operation

retrying.py

class Retrying:
   def __init__(self, interval=1.0, delay=0.05, maxAttempts=None):
      self.interval = interval
      self.delay = delay
      self.maxAttempts = maxAttempts

   def __iter__(self):
      class Iterator:
         def __init__(self, interval, delay, maxAttempts):
            self.attempt = 0

            self.startedAt_ = datetime.now()
            self.interval_ = interval
            self.delay_ = delay
            self.maxAttempts_ = maxAttempts

         def __next__(self):
            time.sleep(self.delay_)
            if self.isExpired() or \
               self.maxAttempts_ and self.attempt >= self.maxAttempts_:
               raise StopIteration
            self.attempt += 1
            return self

         def next(self):
            return self.__next__()

         def isExpired(self):
            return self.interval_ and \
               (datetime.now() - self.startedAt_).total_seconds() > self.interval_

      return Iterator(self.interval, self.delay, self.maxAttempts)

sample usage:

for r in Retrying(interval=self.waitTimeout):
    if self.fileExists():
        return True
    logging.debug('Waiting file %s attempt %d.', self.waitFile, r.attempt)