import inspect

def f(a, b=2, *args, **kwargs): pass

sig = inspect.signature(f)
print(len(sig.parameters))

def add(x):
    def inner(y):
        return x + y
    return inner

print(add(3)(4))

def sum(x, y):
    return x * y

print(sum([1, 2], 2))

def make():
    def f(): return "hi"
    f.data = 42
    return f

g = make()
print(g(), g.data)

log = []

def log_append(x):
    log.append(x)

def runner(func):
    func(1)
    func(2)
    return log

print(runner(log_append))

from typing import Callable

def doubler(f: Callable[[int], int]) -> Callable[[int], int]:
    def wrapped(x: int) -> int:
        return f(x) * 2
    return wrapped

@doubler
def square(x: int) -> int:
    return x * x

print(square(3))

funcs = []
for i in range(3):
    funcs.append(lambda x, i=i: x + i)

print([f(10) for f in funcs])

def collect(n, acc=[]):
    acc.append(n)
    if n == 0:
        return acc
    return collect(n - 1, acc)

print(collect(2), collect(1))

a = [10, 20, 30]
b = [1, 2]

for i, j in zip(enumerate(a), b):
    print(i, j)

class Counter:
    def __init__(self, start, stop):
        self.current = start
        self.stop = stop

    def __iter__(self):
        return self

    def __next__(self):
        if self.current >= self.stop:
            raise StopIteration
        result = self.current
        self.current += 1
        return result

c = Counter(3, 5)
print(list(c))
print(list(c))