الخيوط وGIL

ما الخيط؟

import threading

def worker():
    print('hello from thread')

t = threading.Thread(target=worker)
t.start()
t.join()
print('main done')

بدء عدة خيوط

import threading

def task(name):
    print('task', name)

threads = [threading.Thread(target=task, args=(i,)) for i in range(3)]
for t in threads:
    t.start()
for t in threads:
    t.join()
print('all finished')

قفل المفسّر العام

import sys
print('Running on:', sys.implementation.name)
print('Only one thread runs Python bytecode at a time due to the GIL')

متى تظل الخيوط مفيدة

import threading, time

def fake_io(name):
    time.sleep(0.1)
    print('done', name)

start = time.perf_counter()
ts = [threading.Thread(target=fake_io, args=(i,)) for i in range(3)]
for t in ts: t.start()
for t in ts: t.join()
print('elapsed about 0.1s, not 0.3s')

العمل المقيّد بالمعالج لا يتسارع

import threading

def burn():
    total = 0
    for i in range(1000000):
        total += i
    return total

t = threading.Thread(target=burn)
t.start()
t.join()
print('CPU-bound: threads share one core under the GIL')

الخيوط الخفية

import threading, time

def background():
    time.sleep(0.05)
    print('background tick')

t = threading.Thread(target=background, daemon=True)
t.start()
t.join()
print('main exits')

تسمية الخيوط والتعرّف إليها

import threading

def show():
    t = threading.current_thread()
    print('running in', t.name)

t = threading.Thread(target=show, name='Worker-1')
t.start()
t.join()
print('main thread:', threading.current_thread().name)

إنشاء فئة فرعية من Thread

import threading

class Greeter(threading.Thread):
    def __init__(self, name):
        super().__init__()
        self.who = name
    def run(self):
        print('hi', self.who)

g = Greeter('Sam')
g.start()
g.join()

إعادة النتائج من الخيوط

import threading

results = {}

def compute(key):
    results[key] = key * key

ts = [threading.Thread(target=compute, args=(i,)) for i in range(4)]
for t in ts: t.start()
for t in ts: t.join()
print(results)

عدّ الخيوط النشطة

import threading, time

def wait():
    time.sleep(0.05)

ts = [threading.Thread(target=wait) for _ in range(2)]
for t in ts: t.start()
print('active now:', threading.active_count())
for t in ts: t.join()
print('active after join:', threading.active_count())

اختيار الخيوط أم العمليات

tasks = {'download files': 'threads', 'crunch numbers': 'processes', 'call APIs': 'threads'}
for task, choice in tasks.items():
    print(task, '->', choice)

اختبار سريع

مراجعة