线程

from time import time


def factorize(num):
    for i in range(1, num+1):
        if num % i == 0:
            yield i


nums = [2139079, 1214759, 1516637, 1852285]
start = time()
for num in nums:
    list(factorize(num))
end = time()
print(end-start)


# 0.4892253875732422

from time import time
from threading import Thread


class FactorizeThread(Thread):

    def __init__(self, num):
        super().__init__()
        self.num = num 

    def factorize(self, num):
        for i in range(1, num+1):
            if num % i == 0:
                yield i

    def run(self):
        self.factors = list(self.factorize(self.num))


nums = [2139079, 1214759, 1516637, 1852285]
start = time()
threads = []
for num in nums:
    thread = FactorizeThread(num)
    thread.start()
    threads.append(thread)

for thread in threads:
    thread.join()
end = time()
print(end-start)

# 0.4903602600097656   因为GIl的原因无法真正并行计算

from time import time
from select import select


def slow():
    select([], [], [], 0.1)


start = time()
for _ in range(5):
    slow()
end = time()
print(end-start)

# 0.5008544921875

from time import time
from select import select
from threading import Thread

    
def slow():
    select([], [], [], 0.1)


start = time()
threads = []
for _ in range(5):
    thread = Thread(target=slow)
    thread.start()
    threads.append(thread)

for thread in threads:
    thread.join()
end = time()
print(end-start)

# 0.10056090354919434   处理阻塞式IO速度快5倍
# Python 还有内置的 asyncio 模块来处理阻塞式IO

from threading import Thread


num = 0


def buy():
    global num
    for i in range(1000000):
        num += 1
        
        
threads = []
for _ in range(2):
    thread = Thread(target=buy)
    threads.append(thread)
    thread.start()
    
for thread in threads:
    thread.join()
print(num)

# 1351674  期望是 2000000 

from threading import Thread
from threading import Lock


num = 0 
lock = Lock()


def buy():
    global num 
    for i in range(1000000):
        with lock:
            num += 1


threads = []
for _ in range(2):
    thread = Thread(target=buy)
    threads.append(thread)
    thread.start()

for thread in threads:
    thread.join()
print(num)


# 2000000