How to implement a while loop into this code

I'm currently trying to code this area calulator but I'm having a hard time understanding how to implement a while loop, any help would be appreciated. I have tried looking into loops but I'm not quite understanding how to write them even after watching some YouTube videos.

def calculate_square_area(side:float):
    return side * side

def calculate_rectangele_area(length:float, width:float):
    return length * width

def calculate_circle_area(radius:float):
    pi = 3.14
    return pi * radius **2

def calculate_rhombus_area(p: float, q: float):
    return p*q/2


print("""
---------------
Area Calculator
---------------
""")

selection = input("""\t 'S' - Square
\t 'R'- Rectangle
\t 'C'- Circle
\t 'H'- Rhombus
""")

def calculate_area(selection):
    area = 0
    if selection == "S":
        side =input("Enter The Side:")
        area = calculate_square_area(float(side))
    elif selection == "R":
        length = input ("Enter The Length:")
        width = input ("Enter The Width:")
        area = calculate_rectangele_area(float(length), float(width))
    elif selection == "C":
        radius = input ("Enter The Radius:")
        area = calculate_circle_area(float(radius))
    elif selection == "H":
        p = input("Enter P:")
        q = input ("Enter Q:")
        area = calculate_rhombus_area(float(p), float(q))
           
    else:
        print ("Invalid selection")
        
    return area
        
def get_shape_name(tag):
    shape = "Unkown"
    if tag =="S":
        shape = "Square"
    elif tag == "R":
        shape ="Rectangle"
    elif tag == "C":
        shape = "Circle"
    elif tag == "H":
        shape = "Rhombus"
    return shape  

area = calculate_area(selection)

print(f"The area of the {get_shape_name(selection)} is {area}")

source https://stackoverflow.com/questions/75302476/how-to-implement-a-while-loop-into-this-code