Describe the difference between global and local variables in Python

Global vs Local Variables in Python: Understanding the Difference

Python variables are classified into two main types based on their scope: global variables and local variables.

Global variables:

• Global variables are declared outside of any function or at the top level of a script.
• Their global scope makes them accessible throughout the program.
• A program's global variables are created when it starts and remain in memory until the program ends.
• Any function within the program can access and modify global variables.

Example: Global variable

global_var1 = 250  # This is a global variable
def function_with_global_var():
    print("Global variable value:", global_var1)
function_with_global_var()  # Output: Global variable value: 250

Local variables:

A local variable is one that is declared within a function and has a local scope.

• They are accessible only within the function in which they are defined.
• Local variables are created when the function is called and destroyed when it exits.
• Local variables cannot be accessed from outside the function.

Example: Local variable:

def function_with_local_var():
    local_var = 45  # This is a local variable
    print("Local variable value:", local_var)

function_with_local_var()  # Output: Local variable value: 45
print(local_var)  # Error: NameError - local_var is not defined

Using global variables inside a function:

It is necessary to use the global keyword before the variable name if you want to use a global variable inside a function. This allows you to modify the global variable within the function.

Example: Using a global variable inside a function

global_var = 400
def function_with_global_var():
    global global_var
    global_var += 50
function_with_global_var()
print(global_var)  # Output: 450