Summary - Threading and asyncio

Combine Thread, Lock and ThreadPoolExecutor to write a counter.

Recap: Threading and asyncio

In this group you learned threaded and concurrent programming. You started threads with Thread and protected critical sections with Lock.

You saw how the GIL blocks CPU-bound work. You used a pool with ThreadPoolExecutor. You learned the single-threaded alternative asyncio. Now you will combine these into a threaded counter: a safe counter with Thread and Lock.

Exercise Write a threaded counter

Import with from threading import Thread, Lock. Define count = 0 and lock = Lock(). Write an increment function: global count, lock.acquire(), count += 1, lock.release(). Create a thread with Thread(target=increment), call .start() and .join(). Print count.

Show example solution

from threading import Thread, Lock

count = 0
lock = Lock()

def increment():
    global count
    lock.acquire()
    count += 1
    lock.release()

t = Thread(target=increment)
t.start()
t.join()
print(count)

What you learned

In this group you learned two approaches to concurrent programming in Python. You saw threads with threading and critical section protection with Lock.

You understood how the GIL blocks parallelism for CPU-bound work. You learned pool management with ThreadPoolExecutor. You saw the single-threaded concurrent alternative asyncio. In the summary you combined Thread and Lock into a safe counter.

Test yourself

Match all threading concepts

Thread

Worker thread
Lock

Critical section
GIL

Parallelism barrier
asyncio

Concurrent I/O
Which tool for which job?
- ThreadPoolExecutor for a pool
- Lock to start a thread
- Thread to protect a critical section
- GIL for parallel speedup
Show answer

ThreadPoolExecutor for a pool — answer: ThreadPoolExecutor for a pool. Lock protects, Thread starts, GIL blocks.

Final blank

from threading import Thread, ____
lock = Lock()

Show answer

from threading import Thread, Lock
lock = Lock()

Next lesson: timeit

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