def greet_user2(greeting, name):
    print(greeting, ", ", name, "!", sep="")

def greet_user3(name, greeting='Hello'):
    print(greeting, ", ", name, "!", sep="")
'''
greet_user2("Hello", "Michael")
name = input("Please enter your name: ")
greet_user2('Hi', name)
'''
'''
class Class:
    def __init__(self, val1, val2=None):
        self.__val1 = val1
        if val2 is None:
            self.__val2 = 'Hi'
        self.__val2 = val2
'''
greet_user3('Michael')
greet_user3('Donald', 'Hi')


def append_value(value, array=None, num_times=1):
    if array == None:
        array = []
    while num_times >= 1:
        array.append(value)
        num_times -= 1
    return array

a1 = append_value(5)
print('a1 =', a1)
a2 = append_value(10)
print('a2 =', a2)
print('a1 =', a1)
a3 = []
append_value(13, array=a3)
print('a3 =', a3)
append_value(14, array=a3)
print('a3 =', a3)
print('a2 =', a2)
print('a1 =', a1)
a4 = append_value(15, num_times=3)
print('a4 =', a4)
print('a3 =', a3)
print('a2 =', a2)
print('a1 =', a1)