wrapping python code in main()

The code will not give error on Windows OS if wrapped inside the main function.

Chapter07/multiprocessing/process1.py

@@ -12,20 +12,24 @@ def print_message(msg):
     sleep(1)
     print("{}-{}: {}".format(os.getpid(), cp().name, msg))
 
-processes = []
+def main():
+    processes = []
 
-# creating process
-processes.append(Process(target=print_hello, name="Process 1"))
-processes.append(Process(target=print_hello, name="Process 2"))
-processes.append(Process(target=print_message,
-                         args=["Good morning"], name="Process 3"))
+    # creating process
+    processes.append(Process(target=print_hello, name="Process 1"))
+    processes.append(Process(target=print_hello, name="Process 2"))
+    processes.append(Process(target=print_message,
+                             args=["Good morning"], name="Process 3"))
 
-# start the process
-for p in processes:
-    p.start()
+    # start the process
+    for p in processes:
+        p.start()
 
-# wait till all are done
-for p in processes:
-    p.join()
+    # wait till all are done
+    for p in processes:
+        p.join()
 
-print("Exiting the main process")
+    print("Exiting the main process")
+
+if __name__ == '__main__':
+    main()

Chapter07/multiprocessing/process2.py

@@ -7,9 +7,14 @@ def print_message(msg):
     sleep(1)
     print("{}-{}: {}".format(os.getpid(), cp().name, msg))
 
-# creating process from a pool
-with Pool(3) as proc:
-    proc.map(print_message, ["Orange", "Apple", "Banana",
-                             "Grapes","Pears"])
 
-print("Exiting the main process")
+def main():
+    # creating process from a pool
+    with Pool(3) as proc:
+        proc.map(print_message, ["Orange", "Apple", "Banana",
+                                 "Grapes","Pears"])
+
+    print("Exiting the main process")
+
+if __name__ == '__main__':
+    main()

Chapter07/multiprocessing/process3.py

@@ -10,19 +10,23 @@ def inc_sum_list(list, inc_list, sum):
         inc_list[index] = num + 1
         sum.value = sum.value + inc_list[index]
 
+def main():
 
-mylist = [2, 5, 7]
+    mylist = [2, 5, 7]
 
-inc_list = multiprocessing.Array('i', 3)
+    inc_list = multiprocessing.Array('i', 3)
 
-sum = multiprocessing.Value('i')
+    sum = multiprocessing.Value('i')
 
-p = Process(target=inc_sum_list,
-            args=(mylist, inc_list, sum))
+    p = Process(target=inc_sum_list,
+                args=(mylist, inc_list, sum))
 
-p.start()
-p.join()
-print("incremented list: ", list(inc_list))
-print("sum of inc list: ", sum.value)
+    p.start()
+    p.join()
+    print("incremented list: ", list(inc_list))
+    print("sum of inc list: ", sum.value)
 
-print("Exiting the main process")
+    print("Exiting the main process")
+
+if __name__ == '__main__':
+    main()

Chapter07/multiprocessing/process4.py

@@ -9,21 +9,25 @@ def insert_data (dict1, code, subject):
 def output(dict1):
     print("Dictionary data: ", dict1)
 
-with multiprocessing.Manager() as mgr:
-    # create a dictionary in the server process
-    mydict = mgr.dict({100: "Maths", 200: "Science"})
+def main():
+    with multiprocessing.Manager() as mgr:
+        # create a dictionary in the server process
+        mydict = mgr.dict({100: "Maths", 200: "Science"})
 
-    p1 = Process(target=insert_data, args=(mydict, 300, "English"))
-    p2 = Process(target=insert_data, args=(mydict, 400, "French"))
-    p3 = Process(target=output, args=(mydict,))
+        p1 = Process(target=insert_data, args=(mydict, 300, "English"))
+        p2 = Process(target=insert_data, args=(mydict, 400, "French"))
+        p3 = Process(target=output, args=(mydict,))
 
-    p1.start()
-    p2.start()
+        p1.start()
+        p2.start()
 
-    p1.join()
-    p2.join()
+        p1.join()
+        p2.join()
 
-    p3.start()
-    p3.join()
+        p3.start()
+        p3.join()
 
-print("Exiting the main process")
+    print("Exiting the main process")
+
+if __name__ == '__main__':
+    main()

Chapter07/multiprocessing/process5.py

@@ -11,16 +11,20 @@ def output(myqueue):
     while not myqueue.empty():
         print(myqueue.get())
 
-mylist = [2, 5, 7]
-myqueue = Queue()
+def main():
+    mylist = [2, 5, 7]
+    myqueue = Queue()
 
-p1 = Process(target=copy_data, args=(mylist, myqueue))
-p2 = Process(target=output, args=(myqueue,))
+    p1 = Process(target=copy_data, args=(mylist, myqueue))
+    p2 = Process(target=output, args=(myqueue,))
 
-p1.start()
-p1.join()
-p2.start()
-p2.join()
+    p1.start()
+    p1.join()
+    p2.start()
+    p2.join()
 
-print("Queue is empty: ",myqueue.empty())
-print("Exiting the main process")
+    print("Queue is empty: ",myqueue.empty())
+    print("Exiting the main process")
+
+if __name__ == '__main__':
+    main()

Chapter07/multiprocessing/process6.py

@@ -15,15 +15,20 @@ def myreceiver(r_conn):
             break
         print("Received message : ", msg)
     r_conn.close()
-sender_conn, receiver_conn= Pipe()
 
-p1 = Process(target=mysender, args=(sender_conn, ))
-p2 = Process(target=myreceiver, args=(receiver_conn,))
+def main():
+    sender_conn, receiver_conn= Pipe()
 
-p1.start()
-p2.start()
+    p1 = Process(target=mysender, args=(sender_conn, ))
+    p2 = Process(target=myreceiver, args=(receiver_conn,))
 
-p1.join()
-p2.join()
+    p1.start()
+    p2.start()
 
-print("Exiting the main process")
+    p1.join()
+    p2.join()
+
+    print("Exiting the main process")
+
+if __name__ == '__main__':
+    main()

Chapter07/multiprocessing/process7.py

@@ -9,10 +9,14 @@ def printme (lock, msg):
     finally:
         lock.release()
 
-with Pool(3) as proc:
-    lock = Manager().Lock()
-    func = partial(printme,lock)
-    proc.map(func, ["Orange", "Apple", "Banana",
-                             "Grapes","Pears"])
+def main():
+    with Pool(3) as proc:
+        lock = Manager().Lock()
+        func = partial(printme,lock)
+        proc.map(func, ["Orange", "Apple", "Banana",
+                                 "Grapes","Pears"])
 
-print("Exiting the main process")
+    print("Exiting the main process")
+
+if __name__ == '__main__':
+    main()