class B:
    def __init__(self):
        self.arr = []
    def __getattr__(self, attrname):
        return getattr(self.arr, attrname)
    
b = B()
b.append(1)
b.append(2)
b.append(3)
b.pop()
print(b.arr)

x = float('inf')
s = x - x
print(s)

import numpy as np
import pandas as pd
a = pd.np.array([1, 2, 3])
b = np.array([-3, 2, 1])
print(a @ b)

print(list(map(lambda f: f(2), [lambda x: x**i for i in range(3)])))

print(list(map(lambda f: f(2), (lambda x: x**i for i in range(3)))))

class A:
    def __init__(self):
        self.__x = 1
a = A()

x = 5
y = '5'
print(x == y and not y == x)