Python-多线程

àì夳堔傛蜴生んèń 2022-12-20 06:06 14阅读 0赞

1 多线程是Python程序中实现多任务的一种方式

2 线程是程序执行的最小单元

3 同属于一个进程的多个线程共享进程所拥有的全部资源  
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多线程实现多任务

**1 导入线程模块**  
import threading

**2 通过线程类创建线程对象**  
线程对象 = threading.Thread(target = 任务名）

**3 启动线程执行任务**  
线程对象。start()

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjk4OTczOA_size_16_color_FFFFFF_t_70_pic_center 1]  
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单线程

import threading
    import time
    
    def sing():
        for i in range(3):
            print("...唱歌...")
            time.sleep(1)
    
    def dance():
        for i in range(3):
            print("...跳舞...")
            time.sleep(1)
    
    if __name__ == '__main__':
        sing()
        dance()

改进，多线程

#!/usr/bin/python3.6
    # -*- coding: utf-8 -*-
    # @Time    : 2020/11/11 9:41
    # @Author  : ptg
    # @Email   : zhxwhchina@163.com
    # @File    : 多线程.py
    # @Software: PyCharm
    
    
    import threading
    import time
    
    def sing():
        for i in range(3):
            print("...唱歌...")
            time.sleep(1)
    
    def dance():
        for i in range(3):
            print("...跳舞...")
            time.sleep(1)
    
    if __name__ == '__main__':
        sing_thread = threading.Thread(target=sing)
        dance_thread = threading.Thread(target=dance)
        sing_thread.start()
        dance_thread.start()

#!/usr/bin/python3.6
    # -*- coding: utf-8 -*-
    # @Time    : 2020/11/11 9:41
    # @Author  : ptg
    # @Email   : zhxwhchina@163.com
    # @File    : 多线程.py
    # @Software: PyCharm
    
    
    import threading
    import time
    
    def sing(num):
        for i in range(num):
            print("...唱歌...")
            time.sleep(1)
    
    def dance(count):
        for i in range(count):
            print("...跳舞...")
            time.sleep(1)
        # print("real_time", real_time)
    
    if __name__ == '__main__':
        # start_time = time.time()
        sing_thread = threading.Thread(target=sing,args=(3,))
    
        # 执行任务传递参数
        dance_thread = threading.Thread(target=dance,kwargs={
        "count":2})
        sing_thread.start()
        dance_thread.start()
        # end_time = time.time()
        # real_time = end_time - start_time

主线程结束子线程未结束

import time
    import  threading
    
    def work():
        for i in range(10):
            print("工作...")
            time.sleep(0.2)
    
    if __name__ == '__main__':
        sub_thread = threading.Thread(target=work)
        sub_thread.start()
    
        # 主线程等待1s，后结束
        time.sleep(1)
        print("主线程结束了...")

主线程结束结束后，子线程也相应的结束

#!/usr/bin/python3.6
    # -*- coding: utf-8 -*-
    # @Time    : 2020/11/11 14:48
    # @Author  : ptg
    # @Email   : zhxwhchina@163.com
    # @File    : 主线程和子线程结束顺序.py
    # @Software: PyCharm
    
    
    import time
    import  threading
    
    def work():
        for i in range(10):
            print("工作...")
            time.sleep(0.2)
    
    if __name__ == '__main__':
        # 主线程结束时不想等待子线程程序再结束，可以设置子线程守护主线程
        #   1 threading.Thread(target=work,damon=True
        #   2 线程对象，setDamamon(true)
        sub_thread = threading.Thread(target=work)
        sub_thread.setDaemon(True)
        sub_thread.start()
    
        # 主线程等待1s，后结束
        time.sleep(1)
        print("主线程结束了...")
    
        # 结论：主线程等待结束
        # 守护主线程

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjk4OTczOA_size_16_color_FFFFFF_t_70_pic_center 3]  
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线程执行的顺序

import threading
    
    def task():
        # 获取当前的线程对象
        thread = threading.current_thread()
        print(thread)
    
    if __name__== '__main__':
        for i in range(5):
            sub_thread = threading.Thread(target=task)
            sub_thread.start()

E:\\Anaconda\\envs\\Pytorch\\python.exe E:/PycharmSoftware/project3/线程执行顺序.py  
<Thread(Thread-1, started 996)>  
<Thread(Thread-2, started 21204)>  
<Thread(Thread-3, started 18148)>  
<Thread(Thread-4, started 18684)>  
<Thread(Thread-5, started 19144)>

import threading
    import time
    
    def task():
        time.sleep(1)
        # 获取当前的线程对象
        thread = threading.current_thread()
        print(thread)
    
    if __name__== '__main__':
        for i in range(5):
            sub_thread = threading.Thread(target=task)
            sub_thread.start()
    #         结论：多线程之间执行是无序的，是由CPU调度决定的

=================================================================================================  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80Mjk4OTczOA_size_16_color_FFFFFF_t_70_pic_center 5]  
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多进程实现拷贝copy  
从一个文件夹中拷贝到另一个项目中  
代码如下：

#!/usr/bin/python3.6
    # -*- coding: utf-8 -*-
    # @Time    : 2020/11/9 18:56
    # @Author  : ptg
    # @Email   : zhxwhchina@163.com
    # @File    : mat1.py
    # @Software: PyCharm
    import  os
    import multiprocessing
    
    def copy_file(file_name,source_dir,dest_dir):
        #   1 拼接源文件路径和目标路径
        source_path = source_dir + './' +  file_name
        dest_path = dest_dir +'./' + file_name
    
        #   2 打开源文件和目标文件
        with open(source_path, "rb") as source_file:
            with open(dest_path, "wb") as dest_file:
                #       3 循环读取源文件到目标路径
                while True:
                    data = source_file.read(1024)
                    if data:
                        dest_file.write(data)
                    else:
                        break
    
    if __name__ == '__main__':
    # 1 定义源文件夹和目标文件夹
        source_dir = r'd:\desktop\test'
        dest_dir =r'd:\desktop\dest_dir'
    #
    # 2 创建目标文件夹
        try:
            os.mkdir(dest_dir)
        except:
            print("文件夹已经存在")
    
    # 3 读取源文件夹的文件列表
        file_list = os.listdir(source_dir)
        print(file_list)
    
    # 4 遍历文件列表实现拷贝
        for file_name in file_list:
            copy_file(file_name,source_dir,dest_dir)
    
        # 5 使用多进程实现多任务拷贝
            sub_process = multiprocessing.Process(target=copy_file,args=(file_name,source_dir,dest_dir))
            sub_process.start()

多线程实现文件拷贝

#!/usr/bin/python3.6
    # -*- coding: utf-8 -*-
    # @Time    : 2020/11/9 18:56
    # @Author  : ptg
    # @Email   : zhxwhchina@163.com
    # @File    : mat1.py
    # @Software: PyCharm
    import  os
    import threading
    
    def copy_file(file_name,source_dir,dest_dir):
        #   1 拼接源文件路径和目标路径
        source_path = source_dir + './' +  file_name
        dest_path = dest_dir +'./' + file_name
    
        #   2 打开源文件和目标文件
        with open(source_path, "rb") as source_file:
            with open(dest_path, "wb") as dest_file:
                #       3 循环读取源文件到目标路径
                while True:
                    data = source_file.read(1024)
                    if data:
                        dest_file.write(data)
                    else:
                        break
    
    if __name__ == '__main__':
    # 1 定义源文件夹和目标文件夹
        source_dir = r'd:\desktop\test'
        dest_dir =r'd:\desktop\dest_dir'
    #
    # 2 创建目标文件夹
        try:
            os.mkdir(dest_dir)
        except:
            print("文件夹已经存在")
    
    # 3 读取源文件夹的文件列表
        file_list = os.listdir(source_dir)
        print(file_list)
    
    # 4 遍历文件列表实现拷贝
        for file_name in file_list:
            copy_file(file_name,source_dir,dest_dir)
    
        # 5 使用多进程实现多任务拷贝
            sub_process = threading.Thread(target=copy_file,args=(file_name,source_dir,dest_dir))
            sub_process.start()

（完）！

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