adding chapter 7 source code

Chapter7/multiprocessing/process3.py

@@ -0,0 +1,28 @@
+# process3.py to use shared memory ctype objects
+
+import multiprocessing
+from multiprocessing import Process, Pool, current_process as cp
+
+def inc_sum_list(list, inc_list, sum):
+    sum.value = 0
+
+    for index, num in enumerate(list):
+        inc_list[index] = num + 1
+        sum.value = sum.value + inc_list[index]
+
+
+mylist = [2, 5, 7]
+
+inc_list = multiprocessing.Array('i', 3)
+
+sum = multiprocessing.Value('i')
+
+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)
+
+print("Exiting the main process")