micropython/tests/basics/fun_defargs.py

def fun1(val=5):
    print(val)

fun1()
fun1(10)

def fun2(p1, p2=100, p3="foo"):
    print(p1, p2, p3)

fun2(1)
fun2(1, None)
fun2(0, "bar", 200)
try:
    fun2()
except TypeError:
    print("TypeError")
try:
    fun2(1, 2, 3, 4)
except TypeError:
    print("TypeError")