Python和JavaScript在使用上有什么区别？

冬泳發表於 2021-2-26 09:17:00

Python和JavaScript在使用上有什么区别？

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原文出处：https://www.freecodecamp.org/news/python-vs-javascript-what-are-the-key-differences-between-the-two-popular-programming-languages/
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JavaScript和Python这两种语言非常流行和强大，但它们在部分语法的使用上却有着一些不同，如果你恰好对这些区别对比感兴趣，那么这篇文章中的内容可能会为你提供一些帮助。
在本文中，你将了解到：
<ul>
<li>Python和JavaScript的不同实际应用程序。</li>
<li>Python和JavaScript之间的主要语法和功能差异。</li>
</ul>
<h2>Python VS JavaScript：应用上的差异</h2>
 <img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090324806-1306683467.png" alt="" loading="lazy">
<h3>Python</h3>
由于它的强大和通用性，Python已成为全世界几乎所有科学应用中的重要工具。它是一种通用编程语言，支持不同的编程范式。
它被广泛应用于科学和专业应用，包括数据科学、人工智能、机器学习、计算机科学教育、计算机视觉和图像处理、医学、生物学，甚至天文学。
另外，Python还被用于Web开发，虽然它主要用于后端开发，例如应用程序的服务器端。
<h3>JavaScript</h3>
Python可用于开发Web应用程序的后端部分，但JavaScript可用于开发Web应用程序的后端和前端。
前端是用户看到并与之交互的应用程序的一部分。每当您看到网站或Web应用程序或与之交互时，这部分功能就是JavaScript在 “幕后”提供的。
同样，当你与移动应用进行交互时，您可能会使用JavaScript，因为像React Native这样的框架可以让我们使用JavaScript编写可适应不同平台的应用程序。
JavaScript在Web开发中得到了如此广泛的应用，因为它是一种多功能语言，为我们提供了开发Web应用程序组件所需的工具。
<h3>Python和JavaScript应用程序之间的差异</h3>
简单来讲，从应用程序角度来看，开发人员将Python用于开发科学应用程序，同时使用JavaScript进行Web开发及面向用户的功能和服务器开发。
<h2>Python VS JavaScript: 语法差异</h2>
既然知道了它们在应用层面上用途的区别，那我们就来看看它们的写法和语法上有什么差异，下面我们将通过以下主要元素上的差异。
<ul>
<li>代码块</li>
<li>变量定义</li>
<li>变量命名协议</li>
<li>常量</li>
<li>数据类型和值</li>
<li>注释</li>
<li>内置的数据结构</li>
<li>运算符</li>
<li>输入/输出</li>
<li>条件语句</li>
<li>For循环和While循环</li>
<li>函数</li>
<li>面向对象的编程</li>
</ul>
<h2>Python和JavaScript中的代码块</h2>
每种编程语言都有自己的样式来定义代码块。让我们来看看它们在Python和JavaScript中的区别：
<h3>Python如何定义代码块</h3>
Python依靠缩进来定义代码块。当一系列连续的代码行在同一级别缩进时，它们被视为同一代码块的一部分。
我们使用它来定义Python中的条件、函数、循环和所有的复合语句。
以下是示例：
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090417239-606595672.png" alt="" loading="lazy">
 
在Python中使用缩进定义代码块
<h3>JavaScript如何定义代码块</h3>
在JavaScript中，我们使用花括号（{}）将属于同一代码块的语句分组。
以下是示例：
 <img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091546662-1746029192.png" alt="" loading="lazy">
 
 
 
使用花括号在JavaScript中定义代码块 
<h2>Python和JavaScript中的变量定义</h2>
赋值语句是任何编程语言中最基本的语句之一。让我们看看如何在Python和JavaScript中定义一个变量并对其赋值。
<h3>如何在Python中定义变量</h3>
要在Python中定义变量，我们要写出变量名，后跟等号（=）和将分配给该变量的值。
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;"><variable_name> = <value></pre>
</div>
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">例如
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">x = 5
</pre>
</div>
　
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">如何在JavaScript中定义变量</h3>
语法在JavaScript中非常相似，但是我们只需要var在变量名称之前添加关键字，并以分号（;）结尾即可。　
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">var <variable_name> = <value>;
</pre>
</div>
当使用var定义变量时，该变量具有函数作用域。
<p class="MsoNormal" style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left"> 
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">var x = 5; </pre>
</div>
我们还可以使用关键字let：　　
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">let <variable_name> = <value>; </pre>
</div>
例如：　　
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">let x = 5; </pre>
</div>
当使用let定义变量时，变量将具有块级作用域。它将仅在定义它的代码块中被识别。　　
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090603046-1907284988.png" alt="" loading="lazy">
 
 
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的变量命名约定</h2>
<p style="margin: 0 0 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript遵循两种不同的变量命名约定。
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">如何在Python中命名变量</h3>
<p style="margin: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python推荐使用蛇形命名法（snake_case）。
<p style="margin: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">根据Python样式指南：
<p class="MsoListParagraph" style="margin-left: 21pt; text-indent: -21pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">   变量名遵循与函数名相同的约定。
<p class="MsoListParagraph" style="margin-left: 21pt; text-indent: -21pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">   函数名称应小写，必要时用下划线分隔单词以提高可读性。
<p style="margin: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline"> 
<p style="margin: 0 0 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">因此，Python中的典型变量名称如下所示：
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">first_name </pre>
</div>
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">如何在JavaScript中命名变量</h3>
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">不过在<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">JavaScript<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中，我们应该遵循小骆驼命名法（lowerCamelCase）为命名样式，暨以首字母小写，之后每个新单词以大写字母开头。
根据MDN Web文档的<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">JavaScript<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">准则<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">文章：
对于变量名，请使用lowerCamelCasing，并在适当的地方使用简洁的，易于理解的语义名称。
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">因此，<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">JavaScript<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中的典型变量名称应如下所示：　　
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">firstName
</pre>
</div>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090740810-1390623787.png" alt="" loading="lazy">
 
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的常量</h2>
下面让我们来讨论一下常量。常量是在程序执行期间不能更改的值。
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">如何在Python中定义常量</h3>
<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">在Python中，我们依靠命名规则来定义常量，因为语言中没有严格的规则来防止更改它们的值。
<p style="margin: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">根据Python样式指南：
<p class="MsoNormal" style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">常量通常在模块级别定义，并以所有大写字母书写，并用下划线分隔单词。
<p style="margin: 0 0 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">这是我们用于在Python中定义常量的命名方式：
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">CONSTANT_NAME
</pre>
</div>
例如：
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left"> 
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">TAX_RATE_PERCENTAGE = 32 </pre>
</div>
这样的命名规则只是从规则上为自己和其他开发人员做了约定，该值不应在程序中进行修改，但从技术上讲，该值是可以被更改的。　　
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">如何在JavaScript中定义常量</h3>
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">在JavaScript中，我们可以定义不能在程序中更改的常量，并且不能重新分配变量标识符。
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">但这并不意味着值本身不能更改。
<p style="margin: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">根据这篇文章const的MDN的Web文档：
<p class="MsoNormal" style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">const声明创建了一个对值的只读引用，这并不意味着它所拥有的值是不可改变的--只是变量标识符不能重新分配。例如，在内容是对象的情况下，这意味着对象的内容（例如，它的属性）可以被改变。
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">要在<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">JavaScript<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中定义常量，我们const<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US"> <span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">在变量名称之前添加关键字：
const TAX_RATE_PERCENTAGE = 32;
如果尝试更改常量的值，则会看到此错误：　
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090833485-2127504513.png" alt="" loading="lazy">
 
 <img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090837101-1901164430.png" alt="" loading="lazy">
 
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的数据类型和值</h2>
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">数值数据类型</h3>
<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">Python<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">有三种数值类型，可以帮助我们出于科学目的执行精确计算。这些数值类型包括：int<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US"> (<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">整数)、 float<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">(<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">浮点数)和complex<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">。它们中的每一个都有自己的属性、特征和应用。
<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">而JavaScript只有两种数值类型：Number和BigInt。整数和浮点数都被认为是Number类型。
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">None vs. null</h3>
在Python中，有一个名为None的特殊值，我们通常用它来指示变量在程序中的某个特定点没有值。
<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">JavaScript<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中的等效值为null，这表示不存在任何对象值。
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090847798-1395352054.png" alt="" loading="lazy">
 
 
<h3 style="margin-top: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline"><code>undefined</code> 值</h3>
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">在<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">JavaScript<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">，我们有一个特殊值，当我们声明变量而不分配初始值时会自动分配一个特殊值，它就是<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">undefined<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">。
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">以下是示例：
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090855867-1976229377.png" alt="" loading="lazy">
 
 <span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">在<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">Python<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">，你必须为变量分配一个初始值。没有初始值就无法声明它。你可以讲<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)" lang="EN-US">None<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">指定为<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)" lang="EN-US">Python<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">变量的初始值，以表示缺少值。
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的基础数据类型</h3>
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">基础数据类型表示我们可以在编程语言中处理的最基本的值。让我们比较一下这两种语言的基础数据类型：
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python具有四种基础数据类型：整数（int），浮点数（float），布尔值（bool）和字符串（str）。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">JavaScript具有六种原始数据类型：undefined，布尔值，字符串，数字BigInt和Symbol。</li>
</ul>
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">如何用Python和JavaScript编写注释</h2>
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">注释对于编写简洁易读的代码非常重要。让我们看看在Python和JavaScript中的注释分别是什么样的吧：
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">单行注释</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们使用井号（#）编写注释。该符号之后同一行上的所有字符均被视为注释的一部分。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，我们写两个斜杠（//）来开始单行注释。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090909805-395407067.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">多行注释</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，要编写多行注释，我们要对每一行程序前都加上#号，以标识这行为注释。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，多行注释以/*开头，以*/结束。这些符号之间的所有字符都被视为注释的一部分。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090918114-1300315938.png" alt="" loading="lazy">
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的内置数据结构</h2>
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Tuples</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们有一个内置的数据结构，叫做元组，它和列表非常相似，但是不可更改。因此，它在程序执行过程中不能被改变，所以它被用来存储那些不应该被修改的数据。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，并没有一个内置的具有这些特性的数据结构。虽然你可以通过语言的某些特性来实现类似的数据结构。</li>
</ul>
 <img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090926375-182114081.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">列表List与数组Array</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中， List用于在同一数据结构中存储一系列值。可以在程序中对其进行修改，索引和使用。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，可实现类似功能的数据结构称为Array。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090935151-185607967.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">哈希表</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，有一个称为字典的内置数据结构，可帮助我们将某些值映射到其他值并创建键值对。可用作哈希表使用。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">JavaScript没有这种类型的内置数据结构，但是有某些方法可以使用语言的某些元素来重现其功能。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090942926-1073263618.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">取整除</h3>
<p style="margin: 0 0 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">尽管大多数算术运算符在Python和JavaScript间的工作原理和使用方式完全相同，但在进行整除时却略有不同。
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，用双斜杠（//）进行整除运算。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，没有特定的取整除的运算符。但我们可以通过调用Math.floor()方法将结果四舍五入为最接近的整数。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226090954418-1197673499.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">比较值和类型</h3>
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">在<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">Python<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">，我们使用==<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">运算符比较两个值及其数据类型是否相等。
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;"># Comparing Two Integers
>>> 0 == 0
True
# Comparing Integer to String
>>> 0 == "0"
False </pre>
</div>
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">在<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">JavaScript<span style="border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">，的<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">==<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">运算符，它的执行工作原理是在比较之前将两个对象转换为相同的类型。
<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">如果我们使用<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)" lang="EN-US">JavaScript<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">（<code>0 == "0"</code><span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">）检查上一个示例的<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)" lang="EN-US">“<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">整数与字符串<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)" lang="EN-US">”<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">比较的结果，则结果是True而<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">不是False，<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; color: rgba(10, 10, 35, 1)">因为在比较之前将值转换为相同的数据类型：　　
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091018856-2033608602.png" alt="" loading="lazy">
 
 在JavaScript中，要检查值和数据类型是否相等，我们需要使用另外一个运算符===（三等号）。
<p class="MsoNormal" style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left"> 
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091026274-1193605831.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">逻辑运算符</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，有：and，or，和not这三个逻辑运算符。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，则是：&&，|| 和! 。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091034219-1599946698.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">类型运算符</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，要检查对象的类型，可以使用type()函数。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，我们使用typeof运算符。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091042615-1097935774.png" alt="" loading="lazy">
 
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript的输入和输出</h2>
要求用户输入和向用户显示值在应用中是非常常见的操作。让我们看看在Python和JavaScript中分别是如何表示的。
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">输入</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们使用该input()函数来请求用户输入。我们将消息写在括号内。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，如果是正在浏览器上运行代码可使用prompt作为输入方案（就是这样不是常用方案罢了）， window.prompt(message) 在输入完成后，将结果分配给变量。</li>
</ul>
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">两种方法之间的主要区别在于，在<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">Python<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中，将提示用户在控制台中输入值，而在<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">JavaScript<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">中，浏览器中将显示一个小提示，并要求用户输入值。
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091054610-103544499.png" alt="" loading="lazy">
 
 <img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091100477-39609365.png" alt="" loading="lazy">
 
 在JavaScript中，如果您打开Chrome Developer工具并在控制台中输入以下代码：
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left"> 
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091107631-1656514533.png" alt="" loading="lazy">
 
将显示如下图提示 
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091115578-486021440.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">输出</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们使用print()函数将值打印到控制台。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，我们使用console.log()向控制台打印一个值。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091124772-772647892.png" alt="" loading="lazy">
 
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的条件语句</h2>
<span style="color: rgba(10, 10, 35, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">通过条件语句，我们可以根据特定条件来选择程序后续将要执行的部分。
<h3 style="margin-top: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline"><code>if</code> 语句</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们依靠缩进来指示哪些代码行属于条件代码。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，必须用括号将条件括起来，用花括号将代码括起来。该代码也应缩进。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091134017-897694078.png" alt="" loading="lazy">
 
 
<h3 style="margin-top: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline"><code>if/else</code> 语句</h3>
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">else子句在两种语言中都非常相似。唯一的区别是：
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中， 我们在else关键字之后写一个冒号（:）</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中， <span style="color: rgba(0, 0, 0, 1); background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">我们用大括号({})将属于该子句的代码括起来。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091147772-1346263469.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">多条件语句</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们在条件后面写关键字elif。在条件之后，我们写一个冒号(:)，代码缩进下一行。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，我们编写关键字Else if，后跟条件(用圆括号括起来)。条件结束后，我们编写花括号，并在花括号中缩进代码。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091208182-1405280287.png" alt="" loading="lazy">
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Switch 语句</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline"><span style="color: rgba(0, 0, 0, 1); border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">在JavaScript中，我们有一个额外的控制语句，可以用来根据表达式的值选择要执行的操作。此语句称为switch。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python没有这种类型的语句。</li>
</ul>
 <img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091223582-423687255.png" alt="" loading="lazy">
 
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的For循环和While循环</h2>
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">下面让我们看看如何在Python和JavaScript中定义不同类型的循环以及它们的主要区别。
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">循环</h3>
<p style="margin: 0 0 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中定义for循环的语法比JavaScript中的语法相对简单。
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们在关键字 for 后面写循环变量的名称，关键字 in，及调用 range() 函数，指定必要的参数。然后，我们写一个冒号(:)，后面是缩进的循环主体。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，我们必须明确地指定几个值。我们用for关键字开始，后面是括号。在这些括号中，我们定义了循环变量的初始值，必须为False才能停止循环的条件，以及如何在每次迭代时更新变量。然后，我们写大括号来创建一个代码块，在大括号内我们写出循环的主体缩进。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091234605-734392913.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">遍历可迭代对象</h3>
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">我们可以在Python和JavaScript中使用for循环来迭代可迭代的元素。
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在 Python 中，我们在关键字 for 后面写上循环变量、in 关键字和迭代符。然后，我们写一个冒号（:）和循环的主体（缩进）。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，我们可以使用一个for ... 的循环。我们在for关键字后面写上小括号，在小括号内写上关键字var，后面写上循环变量、关键字of和可迭代。我们用大括号包围循环的主体，然后缩进。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091242577-553994493.png" alt="" loading="lazy">
 
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">While循环</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们在关键字while后面写上条件、冒号(:)，然后在新的一行中写上循环的主体(缩进)。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，语法非常相似。不同的是，我们必须用括号包围条件，用大括号将循环体括起来。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091252277-1832486773.png" alt="" loading="lazy">
 
 
<h3 style="margin-top: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline"><code>do..while</code> 循环</h3>
<p style="margin: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，还有一种Python不存在的循环类型。
<p style="margin: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">这种类型的循环称为do..while循环，因为它至少执行一次操作，并在条件为时继续运行<code>True</code>。
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">do {
// Code
} while (condition); </pre>
</div>
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的函数</h2>
函数对于写出简洁、可维护和可读的程序非常重要。Python和JavaScript中的语法非常相似，但让我们分析一下它们的主要区别：
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在 Python 中，我们在关键字 def 后面写上函数的名称，并在括号中写上参数列表。在这个列表之后，我们写一个冒号（:）和函数的主体（缩进）。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，唯一不同的是，我们使用function关键字定义函数，并在函数的主体周围加上大括号。</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091322193-1794675819.png" alt="" loading="lazy">
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">函数参数的数量</h3>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在 Python 中，传递给函数调用的参数数必须与函数定义中定义的参数数相匹配。如果不是这样，就会发生异常。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline"><span style="color: rgba(0, 0, 0, 1); border: 1pt none rgba(0, 0, 0, 1); padding: 0; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">在JavaScript中，这不是必需的，因为参数是可选的。您可以使用比函数定义中定义的参数更少或更多的参数来调用函数。缺省的参数被赋予未定义的值，额外的参数可以通过Arguments对象访问。</li>
</ul>
 <img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091330395-914873249.png" alt="" loading="lazy">
 
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript进行面向对象的编程</h2>
<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial" lang="EN-US">Python<span style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial">和JavaScript都支持面向对象编程，所以让我们看看如何创建和使用这种编程范例的主要元素。
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Class</h3>
<p class="MsoNormal" style="background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">类定义的第一行在Python和JavaScript中非常相似。我们在关键字class后跟类的名称。
<p class="MsoNormal" style="margin-bottom: 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">唯一的区别是：
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，在类名之后，我们写了一个冒号（:）</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，我们用大括号（{}）括住类的内容</li>
</ul>
<img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091340957-665152408.png" alt="" loading="lazy">
 
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">构造函数和属性</h3>
<p style="margin: 0 0 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">构造函数是一种特殊的方法，当创建类的新实例（新对象）时会调用该方法。它的主要目的是初始化实例的属性。
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，调用了初始化新实例的构造函数init （带有两个前导和尾随下划线）。创建类的实例以初始化其属性时，将自动调用此方法。其参数列表定义了创建实例必须传递的值。该列表以self第一个参数开头。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，构造函数方法被调用，constructor并且它还具有一个参数列表。</li>
</ul>
 <img src="https://img2020.cnblogs.com/blog/139239/202102/139239-20210226091359837-1277806389.png" alt="" loading="lazy">
 
 
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">Python和JavaScript中的方法</h2>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们使用def关键字，其名称和括号内的参数列表定义方法。此参数列表以参数开头，self以引用正在调用该方法的实例。在此列表之后，我们编写一个冒号（:），并将该方法的主体缩进。</li>
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，方法是通过编写其名称，后跟参数列表和花括号来定义的。在花括号内，我们编写方法的主体。</li>
</ul>
<h3 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">实例</h3>
<p style="margin: 0 0 18pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">要创建类的实例：
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="color: rgba(10, 10, 35, 1); text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在Python中，我们编写类的名称，并在括号内传递参数。</li>
</ul>
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">my_circle = Circle(5, "Red")</pre>
</div>
<ul style="margin-top: 0" type="disc">
<li class="MsoNormal" style="text-align: left; line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">在JavaScript中，我们需要new在类名之前添加关键字。</li>
</ul>
<div class="cnblogs_Highlighter">
<pre class="brush:javascript;gutter:true;">my_circle = new Circle(5, "Red");
</pre>
</div>
　　
<h2 style="margin: 6pt 0 2.4pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline">总结</h2>
<p class="MsoNormal" style="line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">Python和JavaScript都是非常强大的语言，因为有着不同的实际应用场景，Python可以用于Web开发和广泛的应用，包括科学用途。JavaScript主要用于Web开发（前端和后端）和移动应用开发。所以，两种语言并没有孰强孰弱的区别。
<p class="MsoNormal" style="line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">虽然它们在语法和使用上有些许区别，但本身作为一门开发语言，使用和掌握上没有本质上的区别，如果有那也只是使用者自身的熟练程度带来的影响罢了。
<p class="MsoNormal" style="line-height: 19.2pt; background-image: initial; background-position: initial; background-size: initial; background-repeat: initial; background-attachment: initial; background-origin: initial; background-clip: initial; vertical-align: baseline" align="left">希望这篇文章能为你带来一些帮助。如果有疑问可以通过评论告诉我。
 

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