from itertools import islice
g = (i**2 for i in range(1, 4))
print(*g[1:3])  # 1
print(*islice(g, 1, 3))  # 2
print(*slice(g, 1, 3))  # 3
print(*g.slice(1, 3))  # 4

class X:
    def __init__(self, l):
        self.l = l
    def __iter__(self):
        return (x for x in self.l)
a = X([1, 2])
b = X([3, 4])
print(*chain(a, a, b, b))

from itertools import repeat, chain
class A:
    def __init__(self, x):
        self.x = x
    def __reversed__(self):
        return chain(reversed(self.x), repeat(0, 2))
a = A([1, 2])
print(*reversed(a))

import re
s = "<span>1</span><b>2</b>"
p1 = re.compile(r"(<\w+>.*</\w+>)")
p2 = re.compile(r"(<\w+>.*?</\w+>)")
x1 = p1.findall(s)
x2 = p2.findall(s)
print(len(x1), len(x2))

import numpy as np
Polynomial = np.polynomial.Polynomial
p = Polynomial([1, -1, 1])
q = Polynomial([2, -3])
print(int((p + q)(1)))

import numpy as np
data = np.array([2, 7, 3, 1])
bins = [0, 5, 10]
hist, _ = np.histogram(data, bins)
print(*hist)
#data - набор данных
#bins - набор интервалов, задаваемых граничными значениями

import numpy as np
x = np.array([1, 2, 3, 4])
print(np.average(x, weights=[2, 1, 0, 5]))

a = [1, 2, 3, 3]
b = {1, 2, 3, 3}
print(set(a) == b, list(b) == a)

class A:
    def __init__(self, value): 
        self.value = value
    def __call__(self, other):
        return self.value ** other
x = A(2) 
print(x(3))

class A:
    def __init__(self, x):
        self.x = x
    def __call__(self):
        return self.x
class B:
    def __init__(self, x):
        self.x = x
    def method(self):
        return self.x
class C:
    def __init__(self, x=3):
        self.x = x
    def __repr__(self):
        return str(self.x)

a = A(1)
b = B(2)
c = C(3)
callables = # ваш код
print([act() for act in callables])

#Вывод:     [1, 2, 3]

def f(arr):
    return arr[0] if len(arr) == 1 else arr[0] + f(arr[1:])
print(f(('a', 'b', 'c', 'd')))