Python学习入门基础教程(learning Python)--4.2 Python的计数循环体for语句
Python的另外一种循环体结构是计数循环体for,通过for循环实现某些语句块循环执行一定次数,其使用语法结构如下。
Python的for循环应用思想和C等其他高级语言一样,当for的条件满足时,for下的语句块执行,不同的是for的条件的写法和其他高级语言有些不太一样。
[python] view plaincopy- for variable in [value1, value2,.....]:
- (TAB)statement
- (TAB)statement
- (TAB)etc.
这里第一次出现了左方括号 ‘[’ 和右方括号 ‘]’, 用左右方括号括起来的数据序列我们称之为list列表,有关list列表的知识我们以后再详细讲解。
这里有一点需要注意就是[value1,value2,.....]后边要有冒号:,否则会有语法出错错误。
for的循环原理是这样的每次从in后边的list取出一个值valuex并赋值for后边variable变量,那循环多少次呢?list里有几个数据就循环几次,当list里的所有数据都取完了,for就结束了,故for执行的次数取决于list里的数据个数,下面我举个例子来说明一下。
[python] view plaincopy
- def main():
- print('I will display the numbers 1 through 5.')
- for num in [1, 2, 3, 4, 5]:
- print(num)
- # Call the main function.
- main()
代码第3行是个for循环每次从[1,2,3,4,5]这个list里取出一个值赋值给num,in后边的list([1, 2, 3, 4, 5])共有5个数据,可知for可以循环5次之后就能结束。
运行结果如下
结下来我们分析一下结果为何是这样的?
每次循环for都会从[ 1, 2, 3, 4, 5]里提取一个数据给num。

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics



PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

VS Code can run on Windows 8, but the experience may not be great. First make sure the system has been updated to the latest patch, then download the VS Code installation package that matches the system architecture and install it as prompted. After installation, be aware that some extensions may be incompatible with Windows 8 and need to look for alternative extensions or use newer Windows systems in a virtual machine. Install the necessary extensions to check whether they work properly. Although VS Code is feasible on Windows 8, it is recommended to upgrade to a newer Windows system for a better development experience and security.

VS Code extensions pose malicious risks, such as hiding malicious code, exploiting vulnerabilities, and masturbating as legitimate extensions. Methods to identify malicious extensions include: checking publishers, reading comments, checking code, and installing with caution. Security measures also include: security awareness, good habits, regular updates and antivirus software.

In VS Code, you can run the program in the terminal through the following steps: Prepare the code and open the integrated terminal to ensure that the code directory is consistent with the terminal working directory. Select the run command according to the programming language (such as Python's python your_file_name.py) to check whether it runs successfully and resolve errors. Use the debugger to improve debugging efficiency.

VS Code can be used to write Python and provides many features that make it an ideal tool for developing Python applications. It allows users to: install Python extensions to get functions such as code completion, syntax highlighting, and debugging. Use the debugger to track code step by step, find and fix errors. Integrate Git for version control. Use code formatting tools to maintain code consistency. Use the Linting tool to spot potential problems ahead of time.

VS Code is available on Mac. It has powerful extensions, Git integration, terminal and debugger, and also offers a wealth of setup options. However, for particularly large projects or highly professional development, VS Code may have performance or functional limitations.

The key to running Jupyter Notebook in VS Code is to ensure that the Python environment is properly configured, understand that the code execution order is consistent with the cell order, and be aware of large files or external libraries that may affect performance. The code completion and debugging functions provided by VS Code can greatly improve coding efficiency and reduce errors.
