Understand Python's global variables and local variables
Understanding Python's global variables and local variables
1. If the variable name inside the defined function appears for the first time and precedes the = symbol, it can be considered to be defined as a local variable. In this case, regardless of whether the variable name is used in the global variable, the local variable is used in the function. For example:
# _*_ coding: utf-8 _*_ num = 110 def func(): num = 1 print(num) func() 输出结果：1
# _*_ coding: utf-8 _*_ num = 110 def func(): num += 1 print(num) func() 输出结果：
UnboundLocalError: local variable 'num' referenced before assignment
Error message: The local variable num is applied before assignment, that is, it is used without defining the variable, thus again It proves that a local variable is defined here instead of using the global num.
Summary: If the variable name inside the function appears for the first time and appears before =, it is regarded as defining a local variable.
2. If the variable name inside the function appears for the first time and appears after =, and the variable has been defined in the global domain, the global variable will be referenced here. If the variable does not exist in the global domain Definition, of course there will be a "variable is not defined" error. For example:
# _*_ coding: utf-8 _*_ num = 110 def func(): num1 = num + 1 print(num1) func() 输出结果： 111 3、函数中使用某个变量时，该变量名既有全局变量也有同名的局部变量，则会使用局部变量，例如：
# _*_ coding: utf-8 _*_ num = 110 def func(): num = 200 num1 = num + 1 print(num1) func() 输出结果： 201
4、在函数中，如果想给全局变量赋值，则需要用关键字global声明，例如：
# _*_ coding: utf-8 _*_ num = 100 def func(): num = 300 num1 = num + 1 print(num1) func() print num 输出结果：
301<br>100
declare num:
# _*_ coding: utf-8 _*_ num = 100 def func(): global num num = 300 num1 = num + 1 print(num1) func() print num
输出结果：
301<br>300
from：
<br>
The above is the detailed content of Understand Python's global variables and local variables. For more information, please follow other related articles on the PHP Chinese website!
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
1658
14
1415
52
1309
25
1257
29
1231
24
PHP and Python: Different Paradigms Explained
Apr 18, 2025 am 12:26 AM
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.
Choosing Between PHP and Python: A Guide
Apr 18, 2025 am 12:24 AM
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 and Python: A Deep Dive into Their History
Apr 18, 2025 am 12:25 AM
PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.
Python vs. JavaScript: The Learning Curve and Ease of Use
Apr 16, 2025 am 12:12 AM
Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.
How to run sublime code python
Apr 16, 2025 am 08:48 AM
To run Python code in Sublime Text, you need to install the Python plug-in first, then create a .py file and write the code, and finally press Ctrl B to run the code, and the output will be displayed in the console.
Where to write code in vscode
Apr 15, 2025 pm 09:54 PM
Writing code in Visual Studio Code (VSCode) is simple and easy to use. Just install VSCode, create a project, select a language, create a file, write code, save and run it. The advantages of VSCode include cross-platform, free and open source, powerful features, rich extensions, and lightweight and fast.
Can visual studio code be used in python
Apr 15, 2025 pm 08:18 PM
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.
How to run python with notepad
Apr 16, 2025 pm 07:33 PM
Running Python code in Notepad requires the Python executable and NppExec plug-in to be installed. After installing Python and adding PATH to it, configure the command "python" and the parameter "{CURRENT_DIRECTORY}{FILE_NAME}" in the NppExec plug-in to run Python code in Notepad through the shortcut key "F6".
