Python Scope

Python Scope （Python作用域）

Understanding Python Scope #

Understanding Python Scope （了解Python作用域）

Python scope refers to the rules that govern how variables and functions are accessed within a Python program. The scope of a variable or function determines where it can be accessed from and how long it will be available. Python has four levels of scope: local, enclosing, global, and built-in. Understanding these levels is crucial for writing Python programs that are efficient, maintainable, and easy to understand.

Local Scope #

Local scope refers to variables that are defined within a function. These variables can only be accessed within the function and are destroyed when the function returns. Local scope is important because it allows you to reuse variable names without worrying about conflicts with other parts of your program. （局部作用域是指在函数中定义的变量。这些变量只能在函数内访问，并在函数返回时被销毁。本地作用域很重要，因为它允许您重用变量名称，而不必担心与程序的其他部分发生冲突。）

graph TD; A(Function) –> B(Local Scope) （A （职能） –> B （本地范围））

Enclosing Scope #

Enclosing scope refers to variables that are defined in an enclosing function. These variables can be accessed by functions nested within the enclosing function. Enclosing scope is useful for creating closures, which are functions that remember the values of their enclosing functions’ variables. （封闭作用域是指在封闭函数中定义的变量。这些变量可以通过嵌套在封闭函数中的函数访问。封闭作用域对于创建闭包非常有用，闭包是记住其封闭函数变量值的函数。）

graph TD; A(Enclosing Function) –> B(Inner Function) （A （封闭功能） –> B （内部功能）） B –> C(Enclosing Scope) （B –> C （封闭范围））

Global Scope #

Global scope refers to variables that are defined outside of any function. These variables can be accessed from any part of your program, including functions. Global scope is useful for defining constants or variables that are used throughout your program. （全局范围是指在任何函数之外定义的变量。可以从程序的任何部分（包括函数）访问这些变量。全局范围对于定义整个程序中使用的常量或变量非常有用。）

graph TD; A(Global Scope) （A （全球范围）） B(Function) –> A （B （功能） –> A）

Built-in Scope #

Built-in scope refers to variables and functions that are built into Python. These variables and functions are available from anywhere in your program. Built-in scope includes functions like print() and len(). （内置作用域是指Python中内置的变量和函数。这些变量和函数可在程序中的任何地方使用。内置范围包括print ()和len ()等函数。）

graph TD; A(Built-in Scope) （A （内置范围））

Using Python Scope #

Using Python Scope （使用Python作用域）

Now that you understand the different levels of Python scope, let’s take a look at how to use them in your programs. （现在您已经了解了Python作用域的不同级别，让我们来看看如何在程序中使用它们。）

Defining Local Variables #

To define a local variable in Python, you simply need to assign a value to it within a function:

def my_function():
   x = 1  # x is a local variable

Accessing Enclosing Variables #

To access a variable from an enclosing function, you can use the nonlocal keyword:

def outer_function():
   x = "outer"

（x = "外部"）
   def inner_function():
       nonlocal x
       x = "inner"

   inner_function()
（inner_function ()）
   print(x)  # Output: inner

Defining Global Variables #

To define a global variable in Python, you can use the global keyword:

global_var = 1  # global variable

def my_function():
   global global_var
   global_var += 1
（global_var + = 1）
   print(global_var)  # Output: 2

Using Built-in Functions #

Built-in functions can be used anywhere in your program:

x = [1, 2, 3]
print(len(x))  # Output: 3

Conclusion #

Conclusion （结论）

Python scope is an important concept that all Python programmers should understand. By using local, enclosing, global, and built-in scope effectively, you can write programs that are efficient, maintainable, and easy to understand. In this article, we’ve provided a comprehensive and detailed overview of Python scope, covering its various levels and how to use them effectively in your programs. （Python作用域是所有Python程序员都应该理解的一个重要概念。通过有效地使用本地、封闭、全局和内置范围，您可以编写高效、可维护且易于理解的程序。在本文中，我们对Python范围进行了全面而详细的概述，涵盖了Python的各个级别以及如何在程序中有效地使用它们。）