26_variable_scope.py

#======================================================================================
#                              Variable Scope
#--------------------------------------------------------------------------------------
# Variable scope tells us where a variable is visible and  available in the code
#======================================================================================

#--------------------------------------------------------------------------------------
# Parameter
#--------------------------------------------------------------------------------------
# A parameter is a variable in a function definition that receives a value when
# the  function is called
#--------------------------------------------------------------------------------------
def greet(text):    # parameter
    print(text)

greet('Hello world')

#--------------------------------------------------------------------------------------
# Local Variable
#--------------------------------------------------------------------------------------
# A local variable is created inside a function and can only be used inside that function
#--------------------------------------------------------------------------------------
def greet():
    message = 'Hello Good Morning!'    # local variable
    print(message)

greet()
#print(message) # local variable cannot be accessed outside the function

#--------------------------------------------------------------------------------------
# Global Variable
#--------------------------------------------------------------------------------------
# A global variable is created outside the functions and can be accessed from anywhere in 
# the program
#--------------------------------------------------------------------------------------
name = "Bob Smith"    # global variable
def greet():
    print(name) # global variable

greet()
print(name)

# Visual understanding
x = 100             # global variable
def display(name):  # parameter
    age = 25        # local variable
    print(name)
    print(age)
    print(x)

display("Frank")
# x --> Global variable (accessible throughout the program)
# name --> Parameter (accessible only inside display() function)
# age --> Local variable (accessible only inside display() function)

# Another example
case_rule = 'lower'     # global variable
def clean_name(name):   # parameter
    cleaned = name.strip()  # local variable
    if case_rule == 'lower':
        cleaned = cleaned.lower()   # local variable
    print(f'Cleaned: {cleaned}')

clean_name('    BOb')
print(f'The rule is {case_rule}')