What are the 4 scope rules in python w3schools

Tom 170 Published: 02/02/2025

What are the 4 scope rules in python w3schools

I'll respond in English as per your request.

In Python, a scope refers to the region of code where a variable is defined and can be accessed. There are four main types of scopes in Python, which are governed by the LEGB rule (Local, Enclosing, Global, Built-in). Here's an explanation of each scope:

Local Scope: A local scope is the smallest scope in Python, where a variable is defined within a function or block of code using the let or var keyword. Local variables are only accessible within that specific scope and cease to exist once the function returns.

For example:

def my_function():
x = 10  # local scope
print(x)  # prints 10
my_function()
print(x)  # NameError: name 'x' is not defined

As you can see, trying to access x outside the function results in a NameError.

Enclosing Scope: An enclosing scope is the next level up from a local scope and refers to the region of code where the current function or block was called. The variable is accessible within that scope and its parent scopes.

For example:

def outer_function():
x = 5   # enclosing scope
def inner_function():
print(x)  # prints 5
inner_function()

In this example, the inner_function has access to the x variable defined in the outer_function, but not outside it.

Global Scope: A global scope is the largest scope in Python and refers to variables that are defined at the top level of a module or script. Global variables are accessible anywhere within that module.

For example:

x = 10  # global scope
def my_function():
print(x)  # prints 10
my_function()
print(x)  # prints 10

In this case, x is a global variable and can be accessed from within the function or outside it.

Built-in Scope: The built-in scope contains Python's built-in functions and variables, such as len(), sum(), and print().

For example:

def my_function():
print(len("hello"))  # prints 5
my_function()

Here, the len() function is accessed from within the function, which is part of the built-in scope.

When you try to access a variable with the same name in multiple scopes, Python follows the LEGB rule:

Local (local scope): If the variable is defined locally, it's used. Enclosing (enclosing scope): If not found locally, Python looks up the parent scope and uses that variable if it exists. Global: If still not found, Python moves up to the global scope and checks if a variable with the same name exists there. Built-in (built-in scope): If still not found, Python defaults to the built-in scope.

Understanding these four scopes is crucial for writing efficient, readable, and maintainable code in Python.

What are the 4 scope rules of variables in Python?

I'm happy to respond in English for you!

In Python, the four scope rules of variables are:

Local Scope: Local variables are defined within a specific block of code (such as inside a function or a loop). They are only accessible within that block and cease to exist once the block is exited.

For example:

def my_function():
x = 5  # local variable
print(x)  # prints 5
print(x)  # error: x is not defined

In this example, x is a local variable within the my_function() function. It is not accessible outside that function.

Global Scope: Global variables are defined at the top level of a Python program and can be accessed from anywhere in the code.

For example:

x = 5  # global variable
def my_function():
print(x)  # prints 5
print(x)  # prints 5

In this example, x is a global variable defined at the top level of the program. It can be accessed from within any function or block of code.

Enclosing Scope: The enclosing scope refers to the scope that surrounds the current scope. This means that if you have a nested function or loop, the variables defined in the outermost scope are accessible to the innermost scope.

For example:

def outer_function():
x = 5
def inner_function():
print(x)  # prints 5
inner_function()
print(x)  # error: x is not defined

In this example, x is a variable defined in the outer_function(), which is accessible within the nested inner_function().

Built-in Scope: Python has several built-in variables and functions that are always available. These include things like print(), len(), and int(). The built-in scope is effectively global, but it's not recommended to use these names as variable names in your own code.

For example:

import math
def my_function():
print(math.pi)  # prints a value representing pi
my_function()

In this example, the math module is imported and its built-in functions (like pi) are accessible within the my_function().

These scope rules help Python manage memory and variables effectively. By understanding how these scopes work, you can write more efficient and readable code.