default values python

def my_function(name, age = 20):
  print(name + " is " + str(age) + " years old"

my_function("Mitro") # Mitro is 20 years old
my_function("Mitro", 26) #Mitro is 26 years old

def your_function(arg,kwarg='default'):
    return arg + kwarg

class Test:
    def __init__(self, val, num = 0):
        self.val = val
        self.num = num

# you can write this:

t = Test(1)
print(t.num) # prints 0

# OR this

t = Test(1, 2)
print(t.num) # prints 2

def F(a, b=None):
    if b is None:
        b = []
    b.append(a)
    return b