all Python 3threadingterm

threading

module

Threads of execution inside one process and synchronisation primitives: Lock, Event, Semaphore, Condition.

Syntax

import threading

Threads help when a program waits on I/O — network, disk; for CPU-bound work on a regular CPython build they bring no speed-up because of the GIL, and multiprocessing is the tool there. For a pool of tasks concurrent.futures.ThreadPoolExecutor is handier. The main mistake is changing shared data without a Lock: the race shows up rarely and cannot be reproduced.

Examples

import threading
results = []
def work(n): results.append(n * n)
threads = [threading.Thread(target=work, args=(i,)) for i in range(4)]
for t in threads: t.start()
for t in threads: t.join()
print(sorted(results))  # → [0, 1, 4, 9]

See also

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