What is the difference between a local variable and a global variable in Python?
Ava W

In Python, local variables and global variables are used to store and access data, but they differ in their scope and accessibility. Here's a detailed explanation of the differences between local and global variables: Local Variables: A local variable is a variable that is declared and defined within a specific function or block of code. It has a limited scope, meaning it is accessible only within the function or block where it is defined. Local variables are created when the function or block is entered and destroyed when it is exited.

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def my_function():
    name = "Alice"
    print(name)

my_function()  # Output: "Alice"
print(name)    # Raises NameError: name 'name' is not defined

In this example, the variablename is a local variable within themy_function() function. It is defined and accessible only within the function. Trying to access thename variable outside of the function raises aNameError because it is out of scope. Local variables are useful for encapsulating data within a specific function or block, preventing unintended changes or conflicts with other variables in different parts of the program. Global Variables: A global variable is a variable that is declared and defined outside of any function or block. It has a global scope, meaning it is accessible from anywhere within the program, including inside functions. Global variables retain their values until they are explicitly changed or the program terminates.

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name = "Alice"

def my_function():
    print(name)

my_function()  # Output: "Alice"
print(name)    # Output: "Alice"

In this example, the variablename is a global variable as it is defined outside of any function. It can be accessed both inside and outside the functionmy_function(). Global variables are useful when you need to share data across multiple functions or blocks within a program. However, using global variables excessively can lead to code that is difficult to maintain and debug. Accessing Global Variables within Functions: If a function needs to access a global variable, you can use theglobal keyword to indicate that the variable being used is a global variable and not a local variable with the same name.

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name = "Alice"

def my_function():
    global name
    name = "Bob"
    print(name)

my_function()  # Output: "Bob"
print(name)    # Output: "Bob"

In this example, theglobal keyword is used within themy_function() function to indicate that thename variable being modified is the global variable. Without theglobal keyword, a new local variable would be created with the same name, and the global variable would remain unchanged. Best Practices: To write clean and maintainable code, it is generally recommended to minimize the use of global variables and instead rely on passing values between functions or using return values. This promotes encapsulation and reduces the risk of variable name conflicts and unintended changes. If you do need to use global variables, it's important to define them in a clear and consistent manner, ensuring they are well-documented and their usage is controlled and limited to where it is necessary. Understanding the differences between local and global variables is crucial for writing reliable and efficient Python code, and choosing the appropriate type of variable depends on the specific needs and scope of the program.

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