多任务就是指：同一时间能执行多个任务。比方我们的电脑能一边QQ聊天，一边写论文，还能听歌。

1.2 多任务的优势：

多任务的最大好处是充分利用CPU资源，提高程序的执行效率。

1.3 多任务的两种表现形式：

（1）并发：

在一段时间内交替去执行多个任务。

例子：

对于单核CPU处理多任务，操作系统轮流让各个任务交替执行。如下图所示：
在这里插入图片描述

（2）并行：

在一段时间内真正的同时一起执行多个任务。

例子：

对于多核cpu处理多任务，操作系统会给cpu的每个内核安排一个执行的任务，多个内核是真正的一起同时执行多个任务。这里需要注意多核cpu是并行的执行多任务，始终有多个任务一起执行。

在这里插入图片描述

二、进程：

在python中，想要实现多任务，可以使用多进程来实现。

2.1 进程的概念：

进程(Process) 是资源分配的最小单位，它是操作系统进行资源分配和调度运行的基本单位，通俗理解: 一个正在运行的程序就是一个进程。例如：正在运行的qq,微信等，他们都是一个进程。
注意：一个正在运行的程序才叫进程，而没有运行的程序，只能叫程序，不能叫进程。
同时，一个程序可以有一个或者多个进程。

2.2 多进程的作用：

在这里插入图片描述

上图中是一个非常简单的程序，一旦运行hello.py这个程序，按照代码的执行顺序, func_ a函数执行完毕后才能执行func_ b函数。如果可以让func a和func _b同时运行,显然执行hello.py这个程序的效率会大大提升。
那怎么实现呢？接着看：

如下图所示，当运行hello.py这个程序的时候，先创建一个主进程，之后再创建了一个子进程，让主进程执行func_a，让子进程执行func_b，这样就使用多进程实现了多任务。

在这里插入图片描述

2.3 多进程完成多任务：

（1）进程的创建步骤：

1、导入进程包：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> multiprocessing
</code></span></span></span></span>

2、通过进程类创建进程对象：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">进程对象 <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>任务名<span style="color:#999999">)</span>
</code></span></span></span></span>

在这里插入图片描述

3、启动进程执行任务：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">进程对象<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

在这里插入图片描述

（2）多进程例子：

下面程序是单进程，先执行唱歌的函数，再执行跳舞的函数。需要3秒完成。

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> time

<span style="color:#6272a4"># 唱歌</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">sing</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 延迟0.5秒</span>
<span style="color:#6272a4"># 跳舞</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">dance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span>
<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    sing<span style="color:#999999">(</span><span style="color:#999999">)</span>
    dance<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

上面的程序怎么使用多进程实现呢？下面的程序实现了多进程实现多任务，我们会发现，只需要1.5秒执行完了，唱歌和跳舞是交替执行的。

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#6272a4"># 1.导入进程包</span>
<span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> multiprocessing


<span style="color:#6272a4"># 唱歌</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">sing</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 延迟0.5秒</span>


<span style="color:#6272a4"># 跳舞</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">dance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 2.使用进程类创建进程对象</span>
    sing_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>sing<span style="color:#999999">)</span>
    dance_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>dance<span style="color:#999999">)</span>

    <span style="color:#6272a4"># 3.使用进程对象启动进程执行指定任务</span>
    sing_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
    dance_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

2.4 进程执行带有参数的任务：

（1）参数说明：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">进程对象 <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>任务名<span style="color:#999999">,</span> args<span style="color:#999999">,</span> kwargs<span style="color:#999999">)</span>
</code></span></span></span></span>

在这里插入图片描述

（2）例子：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#6272a4"># 1.导入进程包</span>
<span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> multiprocessing


<span style="color:#6272a4"># 唱歌</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">sing</span><span style="color:#999999">(</span>num<span style="color:#999999">,</span> name<span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span>num<span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span>name<span style="color:#999999">)</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 延迟0.5秒</span>


<span style="color:#6272a4"># 跳舞</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">dance</span><span style="color:#999999">(</span>num<span style="color:#999999">,</span> name<span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span>num<span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span>name<span style="color:#999999">)</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 2.使用进程类创建进程对象</span>

    <span style="color:#6272a4"># args:使用元组方式给指定任务传参</span>
    sing_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>sing<span style="color:#999999">,</span> args<span style="color:#6272a4">=</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">,</span> <span style="color:#f1fa8c">"李华"</span><span style="color:#999999">)</span><span style="color:#999999">)</span>
    <span style="color:#6272a4"># kwargs:使用字典方式给指定任务传参</span>
    dance_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>dance<span style="color:#999999">,</span> kwargs<span style="color:#6272a4">=</span><span style="color:#999999">{</span><span style="color:#f1fa8c">"num"</span><span style="color:#999999">:</span> <span style="color:#f1fa8c">2</span><span style="color:#999999">,</span> <span style="color:#f1fa8c">"name"</span><span style="color:#999999">:</span><span style="color:#f1fa8c">"小明"</span><span style="color:#999999">}</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 3.使用进程对象启动进程执行指定任务</span>
    sing_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
    dance_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

2.5 获取进程编号：

（1）作用：

当程序中进程的数量越来越多时，如果没有办法区分主进程和子进程还有不同的子进程,那么就无法进行有效的进程管理,为了方便管理实际上每个进程都是有自己的编号。

（2）获取进程编号的两种方式：

（1）获取当前进程编号：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> os

os<span style="color:#999999">.</span>getpid<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

（2）获取当前父进程编号：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> os

os<span style="color:#999999">.</span>getppid<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

（3）例子：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#6272a4"># 1.导入进程包</span>
<span style="color:#ff79c6">import</span> os
<span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> multiprocessing


<span style="color:#6272a4"># 唱歌</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">sing</span><span style="color:#999999">(</span>num<span style="color:#999999">,</span> name<span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌进程编号:"</span><span style="color:#999999">,</span> os<span style="color:#999999">.</span>getpid<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌进程的父进程:"</span><span style="color:#999999">,</span> os<span style="color:#999999">.</span>getppid<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span>

    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span>num<span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span>name<span style="color:#999999">)</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 延迟0.5秒</span>


<span style="color:#6272a4"># 跳舞</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">dance</span><span style="color:#999999">(</span>num<span style="color:#999999">,</span> name<span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞进程编号:"</span><span style="color:#999999">,</span> os<span style="color:#999999">.</span>getpid<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞进程的父进程:"</span><span style="color:#999999">,</span> os<span style="color:#999999">.</span>getppid<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span>

    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span>num<span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span>name<span style="color:#999999">)</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"主进程的编号:"</span><span style="color:#999999">,</span> os<span style="color:#999999">.</span>getpid<span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 2.使用进程类创建进程对象</span>

    <span style="color:#6272a4"># args:使用元组方式给指定任务传参</span>
    sing_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>sing<span style="color:#999999">,</span> args<span style="color:#6272a4">=</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">,</span> <span style="color:#f1fa8c">"李华"</span><span style="color:#999999">)</span><span style="color:#999999">)</span>
    <span style="color:#6272a4"># kwargs:使用字典方式给指定任务传参</span>
    dance_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>dance<span style="color:#999999">,</span> kwargs<span style="color:#6272a4">=</span><span style="color:#999999">{</span><span style="color:#f1fa8c">"num"</span><span style="color:#999999">:</span> <span style="color:#f1fa8c">2</span><span style="color:#999999">,</span> <span style="color:#f1fa8c">"name"</span><span style="color:#999999">:</span><span style="color:#f1fa8c">"小明"</span><span style="color:#999999">}</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 3.使用进程对象启动进程执行指定任务</span>
    sing_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
    dance_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

2.6 进程的注意事项：

（1）主进程会等待所有的子进程完成才结束：

如下图所示，打开QQ时会创建一个主进程，而QQ里面有两个子进程。主进程会等待所有的子进程完成才结束：

在这里插入图片描述

下面看一个例子：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> multiprocessing

<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">work</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 子进程会工作2秒钟</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">10</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"工作中..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.2</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    work_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>work<span style="color:#999999">)</span>
    work_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 主进程睡眠1秒</span>
    time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">1</span><span style="color:#999999">)</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"主进程执行完了..."</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

我们发现，虽然打印了主进程执行完了，但是程序还没有结束，这就说明：主进程会等待所有的子进程完成才结束。

但是我们都知道，当我们把QQ的主进程关闭时，子进程都结束了。那怎么做才能当主进程结束时，子进程也结束了呢？

（2）设置守护主进程：

这个就是说，每一个子进程都守护主进程，当主进程结束了之后，子进程直接结束，也就是被销毁。

只需要加一句话：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">work_process<span style="color:#999999">.</span>daemon <span style="color:#6272a4">=</span> <span style="color:#8be9fd">True</span> <span style="color:#6272a4"># 设置子进程 守护 主进程</span>
</code></span></span></span></span>

看个完整的例子：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> multiprocessing

<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">work</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 子进程会工作2秒钟</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">10</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"工作中..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.2</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    work_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>work<span style="color:#999999">)</span>
    work_process<span style="color:#999999">.</span>daemon <span style="color:#6272a4">=</span> <span style="color:#8be9fd">True</span> <span style="color:#6272a4"># 设置子进程 守护 主进程</span>
    work_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 主进程睡眠1秒</span>
    time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">1</span><span style="color:#999999">)</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"主进程执行完了..."</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

2.7 多进程-案例：

（1）需求分析：

在这里插入图片描述

（2）实现步骤：

在这里插入图片描述

（3）文件的拷贝函数实现步骤：

在这里插入图片描述

（4）实现代码：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> os
<span style="color:#ff79c6">import</span> multiprocessing

<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">copy_file</span><span style="color:#999999">(</span>file_name<span style="color:#999999">,</span> source_dir<span style="color:#999999">,</span> dest_dir<span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 1.拼接源文件路径和目标文件路径</span>
    source_path <span style="color:#6272a4">=</span> source_dir <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">"/"</span> <span style="color:#6272a4">+</span> file_name
    dest_path <span style="color:#6272a4">=</span> dest_dir <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">"/"</span> <span style="color:#6272a4">+</span> file_name

    <span style="color:#6272a4"># 2.打开源文件和目标文件</span>
    <span style="color:#ff79c6">with</span> <span style="color:#f1fa8c">open</span><span style="color:#999999">(</span>source_path<span style="color:#999999">,</span> <span style="color:#f1fa8c">"rb"</span><span style="color:#999999">)</span> <span style="color:#ff79c6">as</span> source_file<span style="color:#999999">:</span>
        <span style="color:#ff79c6">with</span> <span style="color:#f1fa8c">open</span><span style="color:#999999">(</span>dest_path<span style="color:#999999">,</span> <span style="color:#f1fa8c">"wb"</span><span style="color:#999999">)</span> <span style="color:#ff79c6">as</span> dest_file<span style="color:#999999">:</span>
            <span style="color:#6272a4"># 3.循环读取源文件到目标文件</span>
            <span style="color:#ff79c6">while</span> <span style="color:#8be9fd">True</span><span style="color:#999999">:</span>
                data <span style="color:#6272a4">=</span> source_file<span style="color:#999999">.</span>read<span style="color:#999999">(</span><span style="color:#f1fa8c">1024</span><span style="color:#999999">)</span>
                <span style="color:#ff79c6">if</span> data<span style="color:#999999">:</span> <span style="color:#6272a4"># 没到文件的最后一行</span>
                    dest_file<span style="color:#999999">.</span>write<span style="color:#999999">(</span>data<span style="color:#999999">)</span>
                <span style="color:#ff79c6">else</span><span style="color:#999999">:</span> <span style="color:#6272a4"># 为空，则说明到最后一行</span>
                    <span style="color:#ff79c6">break</span>


<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 1.定义源文件夹和目标文件夹</span>
    source_dir <span style="color:#6272a4">=</span> r<span style="color:#f1fa8c">"python视频"</span>
    dest_dir <span style="color:#6272a4">=</span> r<span style="color:#f1fa8c">"/home/python/桌面/test"</span>

    <span style="color:#6272a4"># 2.创建目标文件夹</span>
    <span style="color:#ff79c6">try</span><span style="color:#999999">:</span>
        os<span style="color:#999999">.</span>mkdir<span style="color:#999999">(</span>dest_dir<span style="color:#999999">)</span>
    <span style="color:#ff79c6">except</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"目标文件夹已经存在，未创建"</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 3.读取源文件的文件列表</span>
    file_list <span style="color:#6272a4">=</span> os<span style="color:#999999">.</span>listdir<span style="color:#999999">(</span>source_dir<span style="color:#999999">)</span>

    <span style="color:#6272a4"># 4.遍历文件列表实现拷贝</span>
    <span style="color:#ff79c6">for</span> file_name <span style="color:#ff79c6">in</span> file_list<span style="color:#999999">:</span>
        <span style="color:#6272a4"># copy_file(file_name, source_dir,dest_dir) # 这个实现是单任务的拷贝</span>
        <span style="color:#6272a4"># 5.使用多进程实现多任务拷贝</span>
        sub_process <span style="color:#6272a4">=</span> multiprocessing<span style="color:#999999">.</span>Process<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>copy_file<span style="color:#999999">,</span>
                                              args<span style="color:#6272a4">=</span><span style="color:#999999">(</span>file_name<span style="color:#999999">,</span> source_dir<span style="color:#999999">,</span> dest_dir<span style="color:#999999">)</span><span style="color:#999999">)</span>
        sub_process<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

三、线程：

3.1 线程的介绍：

进程是分配资源的最小单位，一旦创建一个进程就会分配一定的资源，就像跟两个人聊QQ就需要打开两个QQ软件一样是比较浪费资源的。
线程是程序执行的最小单位，实际上进程只负责分配资源，而利用这些资源执行程序的是线程，也就说进程是线程的容器。一个进程中最少有一一个线程来负责执行程序，同时线程自己不拥有系统资源，只需要一点儿在运行中必不可少的资源，但它可与同属一个进程的其它线程共享进程所拥有的全部资源。这就像通过一个QQ软件(一个进程)打开两个窗口(两个线程)跟两个人聊天一样，实现多任务的同时也节省了资源。

3.2 多线程的作用：

在这里插入图片描述

将上图中的程序使用多线程实现，怎么做呢？为此我们先看一下，单线程是怎么实现的：
如下图，单线程是按照顺序实现的，也就是说进程中默认有一个线程用来执行程序，我们称之为主线程。

在这里插入图片描述

如何使用多线程实现呢？和前面的进程一样，用主线程执行func_a，再创建一个子线程执行func_b。

在这里插入图片描述

3.3 多线程实现多任务：

（1）线程的创建步骤：

1、导入线程包：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> threading
</code></span></span></span></span>

2、通过线程类创建线程对象：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">线程对象 <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>任务名<span style="color:#999999">)</span>
</code></span></span></span></span>

在这里插入图片描述

3、启动线程执行任务：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">线程对象<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

（2）多进程例子：

下面程序是单线程，先执行唱歌的函数，再执行跳舞的函数。需要3秒完成。

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> time

<span style="color:#6272a4"># 唱歌</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">sing</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 延迟0.5秒</span>
<span style="color:#6272a4"># 跳舞</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">dance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span>
<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    sing<span style="color:#999999">(</span><span style="color:#999999">)</span>
    dance<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

上面的程序怎么使用多线程实现呢？下面的程序实现了多线程实现多任务，我们会发现，只需要1.5秒执行完了，唱歌和跳舞是交替执行的。

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#6272a4"># 1.导入进程包</span>
<span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> threading


<span style="color:#6272a4"># 唱歌</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">sing</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 延迟0.5秒</span>


<span style="color:#6272a4"># 跳舞</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">dance</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 2.使用进程类创建进程对象</span>
    sing_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>sing<span style="color:#999999">)</span>
    dance_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>dance<span style="color:#999999">)</span>

    <span style="color:#6272a4"># 3.使用进程对象启动进程执行指定任务</span>
    sing_thread<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
    dance_thread<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

3.4 线程执行带有参数的任务：

（1）参数说明：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">进程对象 <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>任务名<span style="color:#999999">,</span> args<span style="color:#999999">,</span> kwargs<span style="color:#999999">)</span>
</code></span></span></span></span>

在这里插入图片描述

（2）例子：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#6272a4"># 1.导入进程包</span>
<span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> threading

<span style="color:#6272a4"># 唱歌</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">sing</span><span style="color:#999999">(</span>num<span style="color:#999999">,</span> name<span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span>num<span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span>name<span style="color:#999999">)</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"唱歌..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 延迟0.5秒</span>

<span style="color:#6272a4"># 跳舞</span>
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">dance</span><span style="color:#999999">(</span>num<span style="color:#999999">,</span> name<span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span>num<span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span>name<span style="color:#999999">)</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"跳舞..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.5</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 2.使用进程类创建进程对象</span>

    <span style="color:#6272a4"># args:使用元组方式给指定任务传参</span>
    sing_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>sing<span style="color:#999999">,</span> args<span style="color:#6272a4">=</span><span style="color:#999999">(</span><span style="color:#f1fa8c">3</span><span style="color:#999999">,</span> <span style="color:#f1fa8c">"李华"</span><span style="color:#999999">)</span><span style="color:#999999">)</span>
    <span style="color:#6272a4"># kwargs:使用字典方式给指定任务传参</span>
    dance_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>dance<span style="color:#999999">,</span> kwargs<span style="color:#6272a4">=</span><span style="color:#999999">{</span><span style="color:#f1fa8c">"num"</span><span style="color:#999999">:</span> <span style="color:#f1fa8c">2</span><span style="color:#999999">,</span> <span style="color:#f1fa8c">"name"</span><span style="color:#999999">:</span><span style="color:#f1fa8c">"小明"</span><span style="color:#999999">}</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 3.使用进程对象启动进程执行指定任务</span>
    sing_thread<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
    dance_thread<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

3.5 主线程和子线程的结束顺序：

（1）主线程会等待所有的子线程完成才结束：

下面的例子说明了主线程会等待所有的子线程完成才结束。

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> threading

<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">work</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 子进程会工作2秒钟</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">10</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"工作中..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.2</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    work_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>work<span style="color:#999999">)</span>
    work_thread<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 主进程睡眠1秒</span>
    time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">1</span><span style="color:#999999">)</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"主线程执行完了..."</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

我们发现，虽然打印了主线程执行完了，但是程序还没有结束，这就说明：主线程会等待所有的子线程完成才结束。

但是我们希望主线程结束了，则所有的子线程都结束，那怎么做呢？接着看：

（2）设置守护主线程：

方法一：
只需要加一句话：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">work_process<span style="color:#999999">.</span>daemon <span style="color:#6272a4">=</span> <span style="color:#8be9fd">True</span> <span style="color:#6272a4"># 设置子线程 守护 主进程</span>
</code></span></span></span></span>

方法二：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python">work_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>work<span style="color:#999999">,</span> daemon<span style="color:#6272a4">=</span><span style="color:#8be9fd">True</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 设置子线程 守护 主进程</span>
</code></span></span></span></span>

看个完整的例子：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> time
<span style="color:#ff79c6">import</span> threading

<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">work</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 子进程会工作2秒钟</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">10</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"工作中..."</span><span style="color:#999999">)</span>
        time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">0.2</span><span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>

    <span style="color:#6272a4"># 方法一：</span>
    work_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>work<span style="color:#999999">,</span> daemon<span style="color:#6272a4">=</span><span style="color:#8be9fd">True</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 设置子进程 守护 主进程</span>

    <span style="color:#6272a4"># 方法二：</span>
    work_thread<span style="color:#999999">.</span>daemon <span style="color:#6272a4">=</span> <span style="color:#8be9fd">True</span> <span style="color:#6272a4"># 设置子进程 守护 主进程</span>
    work_thread<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 主进程睡眠1秒</span>
    time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">1</span><span style="color:#999999">)</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"主线程执行完了..."</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

3.6 线程间的执行顺序：

（1）线程间的执行是无序的：

下图是一个进程创建的三个线程，这三个线程的执行顺序是无序的，与创建的顺序无关，它与操作系统的调度有关。

在这里插入图片描述
看一个例子：

（2）例子：

我们发现，运行的结果和线程的创建顺序并不一样，所以证明：线程间的执行是无序的。

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> threading
<span style="color:#ff79c6">import</span> time

<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">task</span><span style="color:#999999">(</span><span style="color:#999999">)</span><span style="color:#999999">:</span>
    time<span style="color:#999999">.</span>sleep<span style="color:#999999">(</span><span style="color:#f1fa8c">1</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 延迟一秒</span>
    <span style="color:#6272a4"># current_thread:获取当前线程的对象</span>
    thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>current_thread<span style="color:#999999">(</span><span style="color:#999999">)</span> <span style="color:#6272a4"># 获取当前的线程</span>
    <span style="color:#ff79c6">print</span><span style="color:#999999">(</span>thread<span style="color:#999999">)</span>

<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    <span style="color:#ff79c6">for</span> i <span style="color:#ff79c6">in</span> <span style="color:#f1fa8c">range</span><span style="color:#999999">(</span><span style="color:#f1fa8c">5</span><span style="color:#999999">)</span><span style="color:#999999">:</span> <span style="color:#6272a4"># 创建5个线程</span>
        sub_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>task<span style="color:#999999">)</span>
        sub_thread<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>

运行结果：
在这里插入图片描述

3.7 多线程-案例：

（1）需求分析：

在这里插入图片描述

（2）实现：

由于实现的步骤和多进程是一样的，所有接下来直接看代码，注释在代码中：

<span style="color:rgba(0, 0, 0, 0.75)"><span style="background-color:#ffffff"><span style="color:#000000"><span style="background-color:#282a36"><code class="language-python"><span style="color:#ff79c6">import</span> os
<span style="color:#ff79c6">import</span> threading
<span style="color:#ff79c6">def</span> <span style="color:#8be9fd">copy_file</span><span style="color:#999999">(</span>file_name<span style="color:#999999">,</span> source_dir<span style="color:#999999">,</span> dest_dir<span style="color:#999999">)</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 1.拼接源文件路径和目标文件路径</span>
    source_path <span style="color:#6272a4">=</span> source_dir <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">"/"</span> <span style="color:#6272a4">+</span> file_name
    dest_path <span style="color:#6272a4">=</span> dest_dir <span style="color:#6272a4">+</span> <span style="color:#f1fa8c">"/"</span> <span style="color:#6272a4">+</span> file_name

    <span style="color:#6272a4"># 2.打开源文件和目标文件</span>
    <span style="color:#ff79c6">with</span> <span style="color:#f1fa8c">open</span><span style="color:#999999">(</span>source_path<span style="color:#999999">,</span> <span style="color:#f1fa8c">"rb"</span><span style="color:#999999">)</span> <span style="color:#ff79c6">as</span> source_file<span style="color:#999999">:</span>
        <span style="color:#ff79c6">with</span> <span style="color:#f1fa8c">open</span><span style="color:#999999">(</span>dest_path<span style="color:#999999">,</span> <span style="color:#f1fa8c">"wb"</span><span style="color:#999999">)</span> <span style="color:#ff79c6">as</span> dest_file<span style="color:#999999">:</span>
            <span style="color:#6272a4"># 3.循环读取源文件到目标文件</span>
            <span style="color:#ff79c6">while</span> <span style="color:#8be9fd">True</span><span style="color:#999999">:</span>
                data <span style="color:#6272a4">=</span> source_file<span style="color:#999999">.</span>read<span style="color:#999999">(</span><span style="color:#f1fa8c">1024</span><span style="color:#999999">)</span>
                <span style="color:#ff79c6">if</span> data<span style="color:#999999">:</span> <span style="color:#6272a4"># 没到文件的最后一行</span>
                    dest_file<span style="color:#999999">.</span>write<span style="color:#999999">(</span>data<span style="color:#999999">)</span>
                <span style="color:#ff79c6">else</span><span style="color:#999999">:</span> <span style="color:#6272a4"># 为空，则说明到最后一行</span>
                    <span style="color:#ff79c6">break</span>


<span style="color:#ff79c6">if</span> __name__ <span style="color:#6272a4">==</span> <span style="color:#f1fa8c">"__main__"</span><span style="color:#999999">:</span>
    <span style="color:#6272a4"># 1.定义源文件夹和目标文件夹</span>
    source_dir <span style="color:#6272a4">=</span> r<span style="color:#f1fa8c">"python视频"</span>
    dest_dir <span style="color:#6272a4">=</span> r<span style="color:#f1fa8c">"/home/python/桌面/test"</span>

    <span style="color:#6272a4"># 2.创建目标文件夹</span>
    <span style="color:#ff79c6">try</span><span style="color:#999999">:</span>
        os<span style="color:#999999">.</span>mkdir<span style="color:#999999">(</span>dest_dir<span style="color:#999999">)</span>
    <span style="color:#ff79c6">except</span><span style="color:#999999">:</span>
        <span style="color:#ff79c6">print</span><span style="color:#999999">(</span><span style="color:#f1fa8c">"目标文件夹已经存在，未创建"</span><span style="color:#999999">)</span>

    <span style="color:#6272a4"># 3.读取源文件的文件列表</span>
    file_list <span style="color:#6272a4">=</span> os<span style="color:#999999">.</span>listdir<span style="color:#999999">(</span>source_dir<span style="color:#999999">)</span>

    <span style="color:#6272a4"># 4.遍历文件列表实现拷贝</span>
    <span style="color:#ff79c6">for</span> file_name <span style="color:#ff79c6">in</span> file_list<span style="color:#999999">:</span>
        <span style="color:#6272a4"># copy_file(file_name, source_dir,dest_dir) # 这个实现是单任务的拷贝</span>
        <span style="color:#6272a4"># 5.使用多线程实现多任务拷贝</span>
        sub_thread <span style="color:#6272a4">=</span> threading<span style="color:#999999">.</span>Thread<span style="color:#999999">(</span>target<span style="color:#6272a4">=</span>copy_file<span style="color:#999999">,</span>
                                      args<span style="color:#6272a4">=</span><span style="color:#999999">(</span>file_name<span style="color:#999999">,</span> source_dir<span style="color:#999999">,</span> dest_dir<span style="color:#999999">)</span><span style="color:#999999">)</span>
        sub_thread<span style="color:#999999">.</span>start<span style="color:#999999">(</span><span style="color:#999999">)</span>
</code></span></span></span></span>