Adding wait group for process after a question from one of the students.

condition_variables/wait_group_process.py

@@ -0,0 +1,48 @@
+from multiprocessing import Condition, Value, Process
+
+import time
+
+
+# note this is the equivalent of a waitgroup for a process instead of a thread
+class WaitGroupProcess:
+ def __init__(self, cv, wait_count):
+ self.cv = cv
+ self.wait_count = wait_count
+
+ def add(self, count):
+ self.cv.acquire()
+ self.wait_count.value += count
+ self.cv.release()
+
+ def done(self):
+ self.cv.acquire()
+ if self.wait_count.value > 0:
+ self.wait_count.value -= 1
+ if self.wait_count.value == 0:
+ self.cv.notify_all()
+ self.cv.release()
+
+ def wait(self):
+ self.cv.acquire()
+ while self.wait_count.value > 0:
+ self.cv.wait()
+ self.cv.release()
+
+
+def sleep_and_done(condC, wc, time_to_sleep):
+ wg = WaitGroupProcess(condC, wc)
+ time.sleep(time_to_sleep)
+ wg.done()
+ print("Process called done")
+
+
+if __name__ == '__main__':
+ wait_count = Value('i', 0, lock=False)
+ cv = Condition()
+ wait_group_process = WaitGroupProcess(cv, wait_count)
+ wait_group_process.add(3)
+ Process(target=sleep_and_done, args=(cv, wait_count, 2)).start()
+ Process(target=sleep_and_done, args=(cv, wait_count, 5)).start()
+ Process(target=sleep_and_done, args=(cv, wait_count, 7)).start()
+ wait_group_process.wait()
+ print("All processes complete")