Ejercicio clase

def patron(n):
    patron = ""
    for i in range(n,0,-1):
        #Evitar el ultimo salto de linea
        if i > 1:
            patron += "*"*i + "\n"
        else:
            patron += "*"*i


    for i in range(n):
       patron += "*"*i + "\n"

    return patron

print(patron(20))