Python in-memory cache with time to live

Question

I have multiple threads running the same process that need to be able to to notify each other that something should not be worked on for the next n seconds its not the end o

Answer 1

Something like that ?

from time import time, sleep
import itertools
from threading import Thread, RLock
import signal


class CacheEntry():
  def __init__(self, string, ttl=20):
    self.string = string
    self.expires_at = time() + ttl
    self._expired = False

  def expired(self):
    if self._expired is False:
      return (self.expires_at < time())
    else:
      return self._expired

class CacheList():
  def __init__(self):
    self.entries = []
    self.lock = RLock()

  def add_entry(self, string, ttl=20):
    with self.lock:
        self.entries.append(CacheEntry(string, ttl))

  def read_entries(self):
    with self.lock:
        self.entries = list(itertools.dropwhile(lambda x:x.expired(), self.entries))
        return self.entries

def read_entries(name, slp, cachelist):
  while True:
    print "{}: {}".format(name, ",".join(map(lambda x:x.string, cachelist.read_entries())))
    sleep(slp)

def add_entries(name, ttl, cachelist):
  s = 'A'
  while True:
    cachelist.add_entry(s, ttl)
    print("Added ({}): {}".format(name, s))
    sleep(1)
    s += 'A'



if __name__ == "__main__":
  signal.signal(signal.SIGINT, signal.SIG_DFL)

  cl = CacheList()
  print_threads = []
  print_threads.append(Thread(None, read_entries, args=('t1', 1, cl)))
  # print_threads.append(Thread(None, read_entries, args=('t2', 2, cl)))
  # print_threads.append(Thread(None, read_entries, args=('t3', 3, cl)))

  adder_thread = Thread(None, add_entries, args=('a1', 2, cl))
  adder_thread.start()

  for t in print_threads:
    t.start()

  for t in print_threads:
    t.join()

  adder_thread.join()