手把手帶你瞭解python多進程,多線程

說明

相應的學習視頻見鏈接,本文隻對重點進行總結。

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多進程

重點(隻要看下面代碼的main函數即可)

1.創建

2.如何開守護進程

3.多進程,開銷大,用for循環調用多個進程時,後臺cpu一下就上去瞭

import time
import multiprocessing
import os
def dance(who,num):
    print("dance父進程:{}".format(os.getppid()))
    for i in range(1,num+1):
        print("進行編號:{}————{}跳舞。。。{}".format(os.getpid(),who,i))
        time.sleep(0.5)
def sing(num):
    print("sing父進程:{}".format(os.getppid()))
    for i in range(1,num+1):
        print("進行編號:{}----唱歌。。。{}".format(os.getpid(),i))
        time.sleep(0.5)
def work():
    for i in range(10):
        print("工作中。。。")
        time.sleep(0.2)
if __name__ == '__main__':
    # print("main主進程{}".format(os.getpid()))
    start= time.time()
    #1 進程的創建與啟動
    # # 1.1創建進程對象,註意dance不能加括號
    # # dance_process = multiprocessing.Process(target=dance)#1.無參數
    # dance_process=multiprocessing.Process(target=dance,args=("lin",3))#2.以args=元祖方式
    # sing_process = multiprocessing.Process(target=sing,kwargs={"num":3})#3.以kwargs={}字典方式
    # # 1.2啟動進程
    # dance_process.start()
    # sing_process.start()
    #2.默認-主進程和子進程是分開的,主進程隻要1s就可以完成,子進程要2s,主進程會等所有子進程執行完,再退出
    # 2.1子守護主進程,當主一但完成,子就斷開(如qq一關閉,所有聊天窗口就沒瞭).daemon=True
    work_process = multiprocessing.Process(target=work,daemon=True)
    work_process.start()
    time.sleep(1)
    print("主進程完成瞭!")#主進程和子進程是分開的,主進程隻要1s就可以完成,子進程要2s,主進程會等所有子進程執行完,再退出
    print("main主進程花費時長:",time.time()-start)
    #

多線程

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重點

1.創建

2.守護線程

3.線程安全問題(多人搶票,會搶到同一張)

import time
import os
import threading
def dance(num):
    for i in range(num):
        print("進程編號:{},線程編號:{}————跳舞。。。".format(os.getpid(),threading.current_thread()))
        time.sleep(1)
def sing(count):
    for i in range(count):
        print("進程編號:{},線程編號:{}----唱歌。。。".format(os.getpid(),threading.current_thread()))
        time.sleep(1)
def task():
    time.sleep(1)
    thread=threading.current_thread()
    print(thread)
if __name__ == '__main__':
    # start=time.time()
    # # sing_thread =threading.Thread(target=dance,args=(3,),daemon=True)#設置成守護主線程
    # sing_thread = threading.Thread(target=dance, args=(3,))
    # dance_thread = threading.Thread(target=sing,kwargs={"count":3})
    #
    # sing_thread.start()
    # dance_thread.start()
    #
    # time.sleep(1)
    # print("進程編號:{}主線程結束...用時{}".format(os.getpid(),(time.time()-start)))
    for i in range(10):#多線程之間執行是無序的,由cpu調度
        sub_thread = threading.Thread(target=task)
        sub_thread.start()

線程安全

由於線程直接是無序進行的,且他們共享同一個進程的全部資源,所以會產生線程安全問題(比如多人在線搶票,買到同一張)

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#下面代碼在沒有lock鎖時,會賣出0票,加上lock就正常

import threading
import time
lock =threading.Lock()
class Sum_tickets:
    def __init__(self,tickets):
        self.tickets=tickets
def window(sum_tickets):
    while True:
        with lock:
            if sum_tickets.tickets>0:
                time.sleep(0.2)
                print(threading.current_thread().name,"取票{}".format(sum_tickets.tickets))
                sum_tickets.tickets-=1
            else:
                break
if __name__ == '__main__':
    sum_tickets=Sum_tickets(10)
    sub_thread1 = threading.Thread(name="窗口1",target=window,args=(sum_tickets,))
    sub_thread2 = threading.Thread(name="窗口2",target=window,args=(sum_tickets,))
    sub_thread1.start()
    sub_thread2.start()

高並發拷貝(多進程,多線程)

import os
import multiprocessing
import threading
import time
def copy_file(file_name,source_dir,dest_dir):
    source_path = source_dir+"/"+file_name
    dest_path =dest_dir+"/"+file_name
    print("當前進程為:{}".format(os.getpid()))
    with open(source_path,"rb") as source_file:
        with open(dest_path,"wb") as dest_file:
            while True:
                data=source_file.read(1024)
                if data:
                    dest_file.write(data)
                else:
                    break
    pass
if __name__ == '__main__':
    source_dir=r'C:\Users\Administrator\Desktop\註意力'
    dest_dir=r'C:\Users\Administrator\Desktop\test'
    start = time.time()
    try:
        os.mkdir(dest_dir)
    except:
        print("目標文件已存在")
    file_list =os.listdir(source_dir)
    count=0
    #1多進程
    for file_name in file_list:
        count+=1
        print(count)
        sub_processor=multiprocessing.Process(target=copy_file,
                                args=(file_name,source_dir,dest_dir))
        sub_processor.start()
        # time.sleep(20)
    print(time.time()-start)
#這裡有主進程和子進程,通過打印可以看出,主進程在創建1,2,3,4,,,21過程中,子進程已有的開始執行,也就是說,每個進程是互不影響的
# 9
# 10
# 11
# 12
# 13
# 當前進程為:2936(當主進程創建第13個時,此時,第一個子進程開始工作)
# 14
# 當前進程為:10120
# 當前進程為:10440
# 15
# 當前進程為:9508
    # 2多線程
    # for file_name in file_list:
    #     count += 1
    #     print(count)
    #     sub_thread = threading.Thread(target=copy_file,
    #                                             args=(file_name, source_dir, dest_dir))
    #     sub_thread.start()
    #     # time.sleep(20)
    # print(time.time() - start)

總結

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