import numpy as np
a = np.array([1, 2, 3])
b = np.array([4, 5, 6])
c = a + b
c = c * a
print(c[1])

def f(n):
    s = 0
    for i in range(n):
        s += i
        s += ~i
    return s
print(f(1) + f(10) + f(100))

-453492 % 101 + 453492 % 101

class MyList(list):
    def __getitem__(self, index):
        if type(index) is slice:
            index = slice(index.start - 1, index.stop - 1, index.step)
        elif type(index) is int:
            index -= 1
        return list.__getitem__(self, index)

l = MyList(["one", "two", "three", "four", "five", "six"])

print(l[1], l[-1], l[0], l[2:4])

a = 1 * 1
b = 1 / 1
print(a == 1, b == 1, a is 1, b is 1)

import pandas as pd
df = pd.DataFrame()
df['age']  = [36, 43, None]
df['name']  = ['Tom', 'Jone', 'Den']
df[df['age'].isnull()]

class A:
    def __init__(self, x):
        self.x = x
    def __getattribute__(self, name):
        if name == '__add__':
            self.x *= 10
        return object.__getattribute__(self, name)
    def __add__(self, other):
        return self.x + other.x

a1 = A(2)
a2 = A(3) 
print(a1 + a2, a1.__add__(a2))

S = 'abcdef'
print(S.islower() + S.lower().isalpha() + S.isupper())

class A:
    def __getitem__(self, i):
        return i
a = A()
a.__getitem__ = lambda i: i**2

print(a[4])

from functools import reduce
print(reduce(lambda acc, x: x * acc, [1,2,3,4], 1))