def outer(msg):
    def dec(func):
        def wrapper(*args):
            print(msg, end=" ")
            return func(*args)
        return wrapper
    return dec

@outer("hello")
@outer("bye")
def f(x):
    print(x)

f("!")

import time

def timer(func):
    def wrapper():
        start = time.time()
        func()
        end = time.time()
        print("Elapsed:", round(end - start, 2), end=" ")
    return wrapper

@timer
def f():
    time.sleep(0.1)
    print("f done", end=" ")

f()

class dec:
    def __init__(self, func):
        self.func = func
        print("init", end=" ")

    def __call__(self):
        print("before", end=" ")
        self.func()
        print("after", end=" ")

@dec
def f():
    print("f called", end=" ")

f()

def debug(enabled=True):
    def decorator(func):
        def wrapper(*args, **kwargs):
            if enabled:
                print("DEBUG:", func.__name__)
            return func(*args, **kwargs)
        return wrapper
    return decorator

@debug(enabled=False)
def f():
    print("running f")

f()

def gen():
    yield 1
    yield 2
    return 3

g = gen()
try:
    while True:
        print(next(g), end =" ")
except StopIteration as e:
    print("Returned:", e.value)

def repeater(val):
    while True:
        new = yield val
        if new:
            val = new

g = repeater(10)
print(next(g), end =" ")
print(g.send(20), end =" ")
print(next(g), end =" ")

class MyRange:
    def __init__(self, n):
        self.n = n
        self.i = 0
    def __iter__(self):
        return self
    def __next__(self):
        if self.i >= self.n:
            raise StopIteration
        self.i += 1
        return self.i

print(list(MyRange(3)))

def counter():
    i = 0
    while i < 3:
        yield i
        i += 1
    else:
        yield 'done'

print(list(counter()))

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

print(list(tricky()))