import collections
import threading

class ExpiredDeque:
    """Tracks how many events were added in the preceding time period
    """
    def __init__(self, timeout=1):
        self.lock=threading.Lock()
        self.timeout = timeout
        self.events = collections.deque()

    def add(self,item):
        """Add event time
        """
        if item in self:
            print "Cant process the same request from %s in short time (%s sec)" % (item, self.timeout)
            return False

        with self.lock:
            self.events.append(item)
            threading.Timer(self.timeout,self.expire).start()
            return  True

    def __len__(self):
        """Return number of active events
        """
        with self.lock:
            return len(self.events)

    def expire(self):
        """What should we do when value expires
        Remove any expired events
        """
        with self.lock:
            val = self.events.popleft()
            print "expired %s" % val

    def __str__(self):
        with self.lock:
            return str(self.events)

    def __contains__(self, val):
        with self.lock:
            return val in self.events


import time
import datetime
c = ExpiredDeque()
assert(len(c) == 0)
print(c)
# deque([])

c.add('BOB')
c.add('BOB')
time.sleep(0.75)
c.add('SANDY')
assert(len(c) == 2)
print(c)

time.sleep(0.75)
assert(len(c) == 1)
print(c)

time.sleep(0.75)
assert(len(c) == 0)