Variable Scope

A variable scope specifies the region where we can access a variable. 

Local Scope and Local Variables

• A local variable is a variable that is only accessible from within a given function. Such variables are said to have local scope.
• In Python, any variable assigned a value in a function becomes a local variable of the function.

Example

Consider the following example where two functions, func1 and func2, each have a local variable named a:

def func1():
    a = 5  # Local variable 'a' in func1
    print("func1 - a:", a)

def func2():
    a = 10  # Local variable 'a' in func2
    print("func2 before func1 call - a:", a)
    func1()
    print("func2 after func1 call - a:", a)

func2()

Output

func2 before func1 call - a: 10
func1 - a: 5
func2 after func1 call - a: 10

1. Each function has its own local variable a.
2. The value of a in func2 is not affected by the value of a in func1 and vice versa.
3. Calling func1 within func2 does not change the local variable a in func2.

If we remove the assignment of n in func1, it will result in an error because n is not defined within the scope of func1

Lifetime of Local Variables

• The period of time that a variable exists is called its lifetime.
• Local variables are automatically created (allocated memory) when a function is called and destroyed (deallocated) when the function terminates.
• Thus, the lifetime of a local variable is equal to the duration of its function’s execution.
• Consequently, the values of local variables are not retained from one function call to the next.

Global Variables and Global Scope

• A global variable is defined outside any function and can be accessed from multiple functions.
• It has global scope, meaning it's available throughout the entire program.

Example

max_value = 100  # Global variable

def func1():
    print("func1 - max_value:", max_value)

def func2():
    print("func2 - max_value:", max_value)

func1()
func2()

Output

func1 - max_value: 100
func2 - max_value: 100

• max_value is defined outside func1 and func2, making it a global variable.
• Both func1 and func2 can access and print max_value directly.