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<p><img src="https://static.7wate.com/img/2022/11/20/10cf11ddd3b18.png" alt="img"/></p>
<p>函数是通过白盒/黑盒封装多行代码的实现方式，通常具有输入和输出，目的是为了<strong>简化代码</strong>、<strong>重复调用</strong>和<strong>模块化编程</strong>。</p>
<p>在 Python 中，<code>def</code> 关键字用于定义函数，每个函数都具有一个唯一的名称，其命名规则与变量命名规则相同。函数体的第一条语句可以是一个字符串，该字符串被称为<strong>文档字符串</strong>或 docstring，用于提供关于函数的简要描述。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-comment);"># 语法</span></span>
<span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">函数名</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-parameter);">参数列表</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> 函数体</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># 实例</span></span>
<span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">fib</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-parameter);">n</span><span style="color:var(--shiki-color-text);">): </span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);">&quot;&quot;&quot;输出限定数值内的斐波那契数列函数&quot;&quot;&quot;</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> a</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> b </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">0</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">1</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">while</span><span style="color:var(--shiki-color-text);"> a </span><span style="color:var(--shiki-token-keyword);">&lt;</span><span style="color:var(--shiki-color-text);"> n</span><span style="color:var(--shiki-token-punctuation);">:</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(a, end</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-string-expression);">' '</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> a</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> b </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> b</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> a</span><span style="color:var(--shiki-token-keyword);">+</span><span style="color:var(--shiki-color-text);">b</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">()</span></span></code></pre></div>
<h3 id="参数传递">参数传递<a aria-hidden="true" tabindex="-1" href="#参数传递" class="internal"> §</a></h3>
<p>python 中类型属于对象，变量是没有类型的。**python 中一切都是对象，严格意义我们不能说值传递还是引用传递，我们应该说传不可变对象和传可变对象。**而不可变对象和可变对象的区别在于：不可变对象的值不可以改变，而可变对象的值可以改变。</p>
<h4 id="可更改与不可更改对象">可更改与不可更改对象<a aria-hidden="true" tabindex="-1" href="#可更改与不可更改对象" class="internal"> §</a></h4>
<p>在 python 中 strings,、tuples 和 numbers 是不可更改的对象，而 list、dict 等则是可以修改的对象。</p>
<ul>
<li>**不可变类型：**变量赋值 <strong>a=5</strong> 后再赋值 <strong>a=10</strong>，这里实际是新生成一个 int 值对象 10，再让 a 指向它，而 5 被丢弃，不是改变 a 的值，相当于新生成了 a。</li>
<li>**可变类型：**变量赋值 <strong>la=[1,2,3,4]</strong> 后再赋值 <strong>la[2]=5</strong> 则是将 list la 的第三个元素值更改，本身 la 没有动，只是其内部的一部分值被修改了。</li>
</ul>
<h4 id="参数传递-1">参数传递<a aria-hidden="true" tabindex="-1" href="#参数传递-1" class="internal"> §</a></h4>
<ul>
<li>**不可变类型：**类似 C++ 的值传递，如整数、字符串、元组。如 fun(a)，传递的只是 a 的值，没有影响 a 对象本身。如果在 fun(a) 内部修改 a 的值，则是新生成一个 a 的对象。</li>
<li>**可变类型：**类似 C++ 的引用传递，如 列表，字典。如 fun(la)，则是将 la 真正的传过去，修改后 fun 外部的 la 也会受影响</li>
</ul>
<h3 id="默认值参数">默认值参数<a aria-hidden="true" tabindex="-1" href="#默认值参数" class="internal"> §</a></h3>
<p>在 Python 中，函数的参数可以有默认值，也支持使用可变参数，所以 Python 并不需要像其他语言一样支持函数的重载，因为我们在定义一个函数的时候可以让它有多种不同的使用方式。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">add</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-parameter);">a</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">0</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-parameter);">b</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">0</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-parameter);">c</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">0</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);">&quot;&quot;&quot;三个数相加&quot;&quot;&quot;</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">return</span><span style="color:var(--shiki-color-text);"> a </span><span style="color:var(--shiki-token-keyword);">+</span><span style="color:var(--shiki-color-text);"> b </span><span style="color:var(--shiki-token-keyword);">+</span><span style="color:var(--shiki-color-text);"> c</span></span>
<span data-line><span style="color:var(--shiki-token-function);">add</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-token-constant);">3</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># 6</span></span></code></pre></div>
<h3 id="键值参数">键值参数<a aria-hidden="true" tabindex="-1" href="#键值参数" class="internal"> §</a></h3>
<p><code>kwarg=value</code> 形式的 关键字参数 也可以用于调用函数。函数示例如下：</p>
<p>该函数接受一个必选参数（<code>voltage</code>）和三个可选参数（<code>state</code>, <code>action</code> 和 <code>type</code>）。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">parrot</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-parameter);">voltage</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-parameter);">state</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-string-expression);">'a stiff'</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-parameter);">action</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-string-expression);">'voom'</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-parameter);">type</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-string-expression);">'Norwegian Blue'</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-string-expression);">&quot;-- This parrot wouldn't&quot;</span><span style="color:var(--shiki-token-punctuation);">, action, end</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-string-expression);">' '</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-string-expression);">&quot;if you put&quot;</span><span style="color:var(--shiki-token-punctuation);">, voltage, </span><span style="color:var(--shiki-token-string-expression);">&quot;volts through it.&quot;</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-string-expression);">&quot;-- Lovely plumage, the&quot;</span><span style="color:var(--shiki-token-punctuation);">, </span><span style="color:var(--shiki-token-constant);">type</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-string-expression);">&quot;-- It's&quot;</span><span style="color:var(--shiki-token-punctuation);">, state, </span><span style="color:var(--shiki-token-string-expression);">&quot;!&quot;</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-function);">parrot</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-string-expression);">&quot;halo&quot;</span><span style="color:var(--shiki-token-punctuation);">,type</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-string-expression);">&quot;test&quot;</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-comment);"># -- This parrot wouldn't voom if you put halo volts through it.</span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># -- Lovely plumage, the test</span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># -- It's a stiff !</span></span></code></pre></div>
<h3 id="特殊参数">特殊参数<a aria-hidden="true" tabindex="-1" href="#特殊参数" class="internal"> §</a></h3>
<h4 id="可变参数-">可变参数 *<a aria-hidden="true" tabindex="-1" href="#可变参数-" class="internal"> §</a></h4>
<p>在参数名前面的 * 表示 args 是一个可变参数，可以输入多个参数。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">add2</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-keyword);">*</span><span style="color:var(--shiki-token-parameter);">args</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> total </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">0</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">for</span><span style="color:var(--shiki-color-text);"> val </span><span style="color:var(--shiki-token-keyword);">in</span><span style="color:var(--shiki-color-text);"> args</span><span style="color:var(--shiki-token-punctuation);">:</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> total </span><span style="color:var(--shiki-token-keyword);">+=</span><span style="color:var(--shiki-color-text);"> val</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(total)</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-function);">add2</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-token-constant);">3</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># 6</span></span></code></pre></div>
<h4 id="键值参数-">键值参数 **<a aria-hidden="true" tabindex="-1" href="#键值参数-" class="internal"> §</a></h4>
<p>在参数名前面的 ** 表示 args 是一个可变参数，可以输入键值对。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">add2</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-keyword);">**</span><span style="color:var(--shiki-token-parameter);">arg</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(arg)</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-function);">add2</span><span style="color:var(--shiki-token-punctuation);">(name</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-string-expression);">&quot;halo&quot;</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># {'name': 'halo'}</span></span></code></pre></div>
<h4 id="限位置参数-">限位置参数 /<a aria-hidden="true" tabindex="-1" href="#限位置参数-" class="internal"> §</a></h4>
<p><code>/</code> 必须放在形参后面表示限制位置参数，实参必须按照形参位置输入。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">pos_only_arg</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-parameter);">arg</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">/</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(arg)</span></span></code></pre></div>
<h4 id="限关键字参数-">限关键字参数 *<a aria-hidden="true" tabindex="-1" href="#限关键字参数-" class="internal"> §</a></h4>
<p><code>*</code> 必须放在形参前面表示限关键字参数，实参必须按键值参数输入。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">kwd_only_arg</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-keyword);">*</span><span style="color:var(--shiki-color-text);">, </span><span style="color:var(--shiki-token-parameter);">arg</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(arg)</span></span></code></pre></div>
<h4 id="特殊参数组合">特殊参数组合<a aria-hidden="true" tabindex="-1" href="#特殊参数组合" class="internal"> §</a></h4>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">combined_example</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-parameter);">pos_only</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">/</span><span style="color:var(--shiki-color-text);">, </span><span style="color:var(--shiki-token-parameter);">standard</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">*</span><span style="color:var(--shiki-color-text);">, </span><span style="color:var(--shiki-token-parameter);">kwd_only</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(pos_only, standard, kwd_only)</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-comment);">&quot;&quot;&quot;</span></span>
<span data-line><span style="color:var(--shiki-token-comment);">运行示例</span></span>
<span data-line><span style="color:var(--shiki-token-comment);">&quot;&quot;&quot;</span></span>
<span data-line><span style="color:var(--shiki-token-keyword);">>>></span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">combined_example</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-token-punctuation);">, </span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-token-punctuation);">, </span><span style="color:var(--shiki-token-constant);">3</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-token-function);">Traceback </span><span style="color:var(--shiki-token-punctuation);">(most recent call last):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> File </span><span style="color:var(--shiki-token-string-expression);">&quot;&lt;stdin>&quot;</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> line </span><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">in</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">&lt;</span><span style="color:var(--shiki-color-text);">module</span><span style="color:var(--shiki-token-keyword);">></span></span>
<span data-line><span style="color:var(--shiki-token-constant);">TypeError</span><span style="color:var(--shiki-token-punctuation);">:</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">combined_example</span><span style="color:var(--shiki-token-punctuation);">()</span><span style="color:var(--shiki-color-text);"> takes </span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-color-text);"> positional arguments but </span><span style="color:var(--shiki-token-constant);">3</span><span style="color:var(--shiki-color-text);"> were given</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-keyword);">>>></span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">combined_example</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-token-punctuation);">, </span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-token-punctuation);">, kwd_only</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">3</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">3</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-keyword);">>>></span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">combined_example</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-token-punctuation);">, standard</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-token-punctuation);">, kwd_only</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">3</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">3</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-keyword);">>>></span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">combined_example</span><span style="color:var(--shiki-token-punctuation);">(pos_only</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-token-punctuation);">, standard</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">2</span><span style="color:var(--shiki-token-punctuation);">, kwd_only</span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-token-constant);">3</span><span style="color:var(--shiki-token-punctuation);">)</span></span>
<span data-line><span style="color:var(--shiki-token-function);">Traceback </span><span style="color:var(--shiki-token-punctuation);">(most recent call last):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> File </span><span style="color:var(--shiki-token-string-expression);">&quot;&lt;stdin>&quot;</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> line </span><span style="color:var(--shiki-token-constant);">1</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">in</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">&lt;</span><span style="color:var(--shiki-color-text);">module</span><span style="color:var(--shiki-token-keyword);">></span></span>
<span data-line><span style="color:var(--shiki-token-constant);">TypeError</span><span style="color:var(--shiki-token-punctuation);">:</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">combined_example</span><span style="color:var(--shiki-token-punctuation);">()</span><span style="color:var(--shiki-color-text);"> got some positional</span><span style="color:var(--shiki-token-keyword);">-</span><span style="color:var(--shiki-color-text);">only arguments passed </span><span style="color:var(--shiki-token-keyword);">as</span><span style="color:var(--shiki-color-text);"> keyword arguments</span><span style="color:var(--shiki-token-punctuation);">:</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-string-expression);">'pos_only'</span></span></code></pre></div>
<h3 id="return">Return<a aria-hidden="true" tabindex="-1" href="#return" class="internal"> §</a></h3>
<p><strong>return [表达式]</strong> 语句用于退出函数，选择性地向调用方返回一个表达式。不带参数值的 return 语句返回 None。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">sum</span><span style="color:var(--shiki-color-text);">( </span><span style="color:var(--shiki-token-parameter);">arg1</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-parameter);">arg2</span><span style="color:var(--shiki-color-text);"> ):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 返回2个参数的和.&quot;</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> total </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> arg1 </span><span style="color:var(--shiki-token-keyword);">+</span><span style="color:var(--shiki-color-text);"> arg2</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print </span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-string-expression);">&quot;函数内 : &quot;</span><span style="color:var(--shiki-token-punctuation);">, total)</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">return</span><span style="color:var(--shiki-color-text);"> total</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># 调用sum函数</span></span>
<span data-line><span style="color:var(--shiki-color-text);">total </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">sum</span><span style="color:var(--shiki-token-punctuation);">( </span><span style="color:var(--shiki-token-constant);">10</span><span style="color:var(--shiki-token-punctuation);">, </span><span style="color:var(--shiki-token-constant);">20</span><span style="color:var(--shiki-token-punctuation);"> )</span></span>
<span data-line><span style="color:var(--shiki-token-function);">print </span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-string-expression);">&quot;函数外 : &quot;</span><span style="color:var(--shiki-token-punctuation);">, total)</span></span></code></pre></div>
<h2 id="全局局部变量">全局、局部变量<a aria-hidden="true" tabindex="-1" href="#全局局部变量" class="internal"> §</a></h2>
<p>在 Python 中，变量的作用范围可分为全局变量和局部变量。</p>
<ul>
<li>**全局变量：**在函数体外部声明的变量被称为全局变量。全局变量在程序的整个生命周期内都是可访问的。</li>
<li>**局部变量：**在函数体内部声明的变量被称为局部变量。它们只能在声明它们的函数内部被访问。</li>
</ul>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-color-text);">x </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">10</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 这是一个全局变量</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">func</span><span style="color:var(--shiki-color-text);">():</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> y </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">5</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 这是一个局部变量</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(y)</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 输出：5</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-function);">func</span><span style="color:var(--shiki-token-punctuation);">()</span></span>
<span data-line><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(x)</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 输出：10</span></span>
<span data-line><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(y)</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 将会引发一个错误，因为 y 在这个作用域内不存在</span></span></code></pre></div>
<h2 id="globalnonlocal">global、nonlocal<a aria-hidden="true" tabindex="-1" href="#globalnonlocal" class="internal"> §</a></h2>
<p>当需要在函数或其他作用域内部改变全局变量或嵌套作用域中的变量时，我们需要使用 <code>global</code> 或 <code>nonlocal</code> 关键字。</p>
<ul>
<li><strong>global 关键字：</strong> 允许你在函数或其他局部作用域内部修改全局变量。</li>
<li><strong>nonlocal 关键字：</strong> 允许你在嵌套的函数（即闭包）中修改上一层非全局作用域的变量。</li>
</ul>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-comment);"># 使用 global 关键字：</span></span>
<span data-line><span style="color:var(--shiki-color-text);">x </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">10</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">func</span><span style="color:var(--shiki-color-text);">():</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">global</span><span style="color:var(--shiki-color-text);"> x</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> x </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">20</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 修改全局变量 x</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-function);">func</span><span style="color:var(--shiki-token-punctuation);">()</span></span>
<span data-line><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(x)</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 输出：20</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-comment);"># 使用 nonlocal 关键字：</span></span>
<span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">outer</span><span style="color:var(--shiki-color-text);">():</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> x </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">10</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">inner</span><span style="color:var(--shiki-color-text);">():</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">nonlocal</span><span style="color:var(--shiki-color-text);"> x</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> x </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">20</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 修改上一层函数中的 x</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">inner</span><span style="color:var(--shiki-token-punctuation);">()</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(x)</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 输出：20</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-function);">outer</span><span style="color:var(--shiki-token-punctuation);">()</span></span></code></pre></div>
<h2 id="yield">Yield<a aria-hidden="true" tabindex="-1" href="#yield" class="internal"> §</a></h2>
<p><code>yield</code> 是 Python 中用于创建生成器（generator）的关键字。一个包含 <code>yield</code> 表达式的函数被称为一个生成器函数。这种函数在被调用时不会立即执行，而是返回一个迭代器，这个迭代器可以在其元素需要被处理时生成它们。这种延迟生成元素的方式使得生成器在处理大数据集或无限序列时非常有用，因为它们不需要一次性生成所有元素，从而节省内存。</p>
<p>生成器函数在执行到 <code>yield</code> 表达式时会暂停并保存当前所有的状态信息（包括局部变量等），在下次从该函数获取下一个元素（即进行下一次迭代）时，它会从保存的状态和位置继续执行。</p>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-comment);"># yield a 语句会暂停函数的执行并返回当前的 a 值作为序列的下一个元素。</span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># 在下次迭代时，函数会从 yield a 语句后的语句继续执行，计算出序列的下一个值。</span></span>
<span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">fibonacci</span><span style="color:var(--shiki-color-text);">():</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> a</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> b </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">0</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">1</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">while</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">True</span><span style="color:var(--shiki-token-punctuation);">:</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">yield</span><span style="color:var(--shiki-color-text);"> a</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> a</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> b </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> b</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> a </span><span style="color:var(--shiki-token-keyword);">+</span><span style="color:var(--shiki-color-text);"> b</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-comment);"># zip(range(10), fibonacci()) 部分会生成一个迭代器</span></span>
<span data-line><span style="color:var(--shiki-token-comment);"># 这个迭代器在每次迭代时都会返回斐波那契数列的下一个数字，直到生成了前 10 个数字为止。</span></span>
<span data-line><span style="color:var(--shiki-token-keyword);">for</span><span style="color:var(--shiki-color-text);"> _</span><span style="color:var(--shiki-token-punctuation);">,</span><span style="color:var(--shiki-color-text);"> val </span><span style="color:var(--shiki-token-keyword);">in</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">zip</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-function);">range</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-constant);">10</span><span style="color:var(--shiki-token-punctuation);">), </span><span style="color:var(--shiki-token-function);">fibonacci</span><span style="color:var(--shiki-token-punctuation);">()):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(val)</span></span></code></pre></div>
<h2 id="lambda">Lambda<a aria-hidden="true" tabindex="-1" href="#lambda" class="internal"> §</a></h2>
<p>lambda 关键字用于创建小巧的匿名函数。Lambda 函数可用于任何需要函数对象的地方。在语法上，匿名函数只能是单个表达式。在语义上，它只是常规函数定义的语法糖。与嵌套函数定义一样，lambda 函数可以引用包含作用域中的变量：</p>
<ul>
<li><strong>lambda</strong> 只是一个表达式，函数体比 <strong>def</strong> 简单很多。</li>
<li>lambda 的主体是一个表达式，而不是一个代码块。仅仅能在 lambda 表达式中封装有限的逻辑进去。</li>
<li>lambda 函数拥有自己的命名空间，且不能访问自己参数列表之外或全局命名空间里的参数。</li>
<li>虽然 lambda 函数看起来只能写一行，却不等同于 C 或 C++ 的内联函数，后者的目的是调用小函数时不占用栈内存从而增加运行效率。</li>
</ul>
<div data-rehype-pretty-code-fragment><pre style="background-color:var(--shiki-color-background);" tabindex="0" data-language="python" data-theme="default"><code data-language="python" data-theme="default"><span data-line><span style="color:var(--shiki-token-comment);"># 语法</span></span>
<span data-line><span style="color:var(--shiki-token-keyword);">lambda</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-parameter);">arguments</span><span style="color:var(--shiki-color-text);">: expression</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-comment);"># lambda 实例</span></span>
<span data-line><span style="color:var(--shiki-color-text);">double </span><span style="color:var(--shiki-token-keyword);">=</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">lambda</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-parameter);">x</span><span style="color:var(--shiki-color-text);">: x </span><span style="color:var(--shiki-token-keyword);">*</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">2</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-comment);"># 常规函数</span></span>
<span data-line><span style="color:var(--shiki-token-keyword);">def</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-function);">double</span><span style="color:var(--shiki-color-text);">(</span><span style="color:var(--shiki-token-parameter);">x</span><span style="color:var(--shiki-color-text);">):</span></span>
<span data-line><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-keyword);">return</span><span style="color:var(--shiki-color-text);"> x </span><span style="color:var(--shiki-token-keyword);">*</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-constant);">2</span></span>
<span data-line> </span>
<span data-line><span style="color:var(--shiki-token-function);">print</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-function);">double</span><span style="color:var(--shiki-token-punctuation);">(</span><span style="color:var(--shiki-token-constant);">5</span><span style="color:var(--shiki-token-punctuation);">))</span><span style="color:var(--shiki-color-text);"> </span><span style="color:var(--shiki-token-comment);"># 输出：10</span></span></code></pre></div></article></div><div class="right sidebar"><div class="graph "><h3>Graph View</h3><div class="graph-outer"><div id="graph-container" data-cfg="{&quot;drag&quot;:true,&quot;zoom&quot;:true,&quot;depth&quot;:1,&quot;scale&quot;:1.1,&quot;repelForce&quot;:0.5,&quot;centerForce&quot;:0.3,&quot;linkDistance&quot;:30,&quot;fontSize&quot;:0.6,&quot;opacityScale&quot;:1,&quot;showTags&quot;:true,&quot;removeTags&quot;:[]}"></div><svg version="1.1" id="global-graph-icon" xmlns="http://www.w3.org/2000/svg" xmlnsXlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewBox="0 0 55 55" fill="currentColor" xmlSpace="preserve"><path d="M49,0c-3.309,0-6,2.691-6,6c0,1.035,0.263,2.009,0.726,2.86l-9.829,9.829C32.542,17.634,30.846,17,29,17
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