def tricky():
    yield from range(2)
    yield from "ab"

print(list(tricky()))

def chain():
    yield from [1, 2]
    yield from (x for x in range(2))

print(list(chain()))

def inner():
    yield from [1, 2]

def outer():
    yield from inner()

print(list(outer()))

def step():
    for i in range(2):
        yield i
    yield from "xy"

print(list(step()))

def gen():
    yield from []
    yield 42

print(next(gen()))

def add_to(val, lst=[]):
    lst.append(val)
    return lst

print(add_to(1), end = " ")
print(add_to(2))

def f(a, b=2, c=3):
    print(a, b, c)

f(1, c=10)

def f(x=[]):
    x += [1]
    return x

print(f(), end = " ")
print(f())

def f(a, *args, b=5, **kwargs):
    print(a, args, b, kwargs)

f(1, 2, 3, x=7, y=8)

def f():
    return

print(f() is None)