Updated code examples for latest version of the book

Author: SuperFastPython

src/lesson01_pool.py

@@ -2,17 +2,17 @@
 # example running a function in the multiprocessing pool
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task():
+    # report a message
     print('This is another process', flush=True)
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
-    pool = Pool()
-    # issue the task
-    async_result = pool.apply_async(task)
-    # wait for the task to finish
-    async_result.wait()
-    # close the multiprocessing pool
-    pool.close()
+    with Pool() as pool:
+        # issue the task
+        async_result = pool.apply_async(task)
+        # wait for the task to finish
+        async_result.wait()
+    # close the multiprocessing pool automatically

src/lesson01_process.py

@@ -2,15 +2,16 @@
 # example of running a function in a new process
 from multiprocessing import Process
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task():
+    # report a message
     print('This is another process', flush=True)
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # define a task to run in a new process
     process = Process(target=task)
     # start the task in a new process
     process.start()
-    # wait for the task to complete
+    # wait for the child process to terminate
     process.join()

src/lesson02_initalizer.py

@@ -3,7 +3,7 @@
 from time import sleep
 from multiprocessing import Pool
 
-# task executed in a worker process
+# custom function to be executed in a child process
 def task():
     # report a message
     print('Worker executing task...', flush=True)

src/lesson03_apply.py

@@ -1,12 +1,13 @@
 # SuperFastPython.com
-# example of executing a task with Pool.apply()
+# example of executing a one-off task and waiting
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task():
+    # report a message
     print('This is another process', flush=True)
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool() as pool:

src/lesson03_map.py

@@ -1,15 +1,15 @@
 # SuperFastPython.com
-# example of executing multiple task with Pool.map()
+# example of executing multiple tasks and waiting
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task(arg):
     # report a message
     print(f'From another process {arg}', flush=True)
     # return a value
     return arg * 2
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool() as pool:

src/lesson03_starmap.py

@@ -2,15 +2,15 @@
 # example of multiple tasks with multiple arguments
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task(arg1, arg2, arg3):
     # report a message
     print(f'From another process {arg1}, {arg2}, {arg3}',
         flush=True)
     # return a value
     return arg1 + arg2 + arg3
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool() as pool:

src/lesson04_apply_async.py

@@ -1,12 +1,13 @@
 # SuperFastPython.com
-# example of executing a task with Pool.apply_async()
+# example of executing a one-off task asynchronously
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task():
+    # report a message
     print('This is another process', flush=True)
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool() as pool:

src/lesson04_map_async.py

@@ -1,15 +1,15 @@
 # SuperFastPython.com
-# example executing multiple task with Pool.map_async()
+# example executing multiple tasks asynchronously
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task(arg):
     # report a message
     print(f'From another process {arg}', flush=True)
     # return a value
     return arg * 2
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool() as pool:

src/lesson04_starmap_async.py

@@ -1,16 +1,16 @@
 # SuperFastPython.com
-# example with multiple tasks with multiple arguments
+# example many tasks multiple arguments asynchronously
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task(arg1, arg2, arg3):
     # report a message
     print(f'From another process {arg1}, {arg2}, {arg3}',
         flush=True)
     # return a value
     return arg1 + arg2 + arg3
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool() as pool:

src/lesson05_imap.py

@@ -1,10 +1,10 @@
 # SuperFastPython.com
-# example of executing multiple task with Pool.imap()
+# example of executing multiple tasks one-by-one
 from time import sleep
 from random import random
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task(arg):
     # block for a random fraction of a second
     sleep(random())
@@ -13,7 +13,7 @@ def task(arg):
     # return a value
     return arg * 2
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool(4) as pool:

src/lesson05_imap_unordered.py

@@ -1,10 +1,10 @@
 # SuperFastPython.com
-# example executing multiple task with imap_unordered()
+# example getting many task results in completion order
 from time import sleep
 from random import random
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task(arg):
     # block for a random fraction of a second
     sleep(random())
@@ -13,7 +13,7 @@ def task(arg):
     # return a value
     return arg * 2
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool(4) as pool:

src/lesson06_asyncresult.py

@@ -4,7 +4,7 @@
 from random import random
 from multiprocessing import Pool
 
-# a task to execute in another process
+# custom function to be executed in a child process
 def task():
     # loop a few times to simulate a slow task
     for i in range(10):
@@ -15,7 +15,7 @@ def task():
         # report a message
         print(f'>{i} got {value}', flush=True)
 
-# entry point for the program
+# protect the entry point
 if __name__ == '__main__':
     # create the multiprocessing pool
     with Pool() as pool:

src/lesson06_callback.py

@@ -1,11 +1,12 @@
 # SuperFastPython.com
-# example of a callback function for Pool.apply_async()
+# example of callback function for a one-off async task
 from random import random
 from time import sleep
 from multiprocessing.pool import Pool
 
-# result callback function
+# custom function to be executed in a child process
 def result_callback(return_value):
+    # report a message
     print(f'Callback got: {return_value}', flush=True)
 
 # task executed in a worker process

src/lesson07_check_prime_parallel.py

@@ -37,7 +37,7 @@ def check_numbers_are_prime(numbers):
             if isprime:
                 print(f'{number} is prime')
 
-# entry point
+# protect the entry point
 if __name__ == '__main__':
     # define some numbers to check
     NUMS = [17977, 10619863, 106198, 6620830889,

src/lesson07_check_prime_sequential.py

@@ -32,7 +32,7 @@ def check_numbers_are_prime(numbers):
         if is_prime(number):
             print(f'{number} is prime')
 
-# entry point
+# protect the entry point
 if __name__ == '__main__':
     # define some numbers to check
     NUMS = [17977, 10619863, 106198, 6620830889,
@@ -43,4 +43,3 @@ def check_numbers_are_prime(numbers):
         44560482149, 1746860020068409]
     # check whether each number is a prime
     check_numbers_are_prime(NUMS)
-