import numpy as np
matrix = np.array([[1, 2, 3],
                   [4, 5, 6],
                   [7, 8, 9]])
print(matrix[1, 1])

s[: : -1]

''.join(reversed(s))

s1 = ''
for char in s:
    s1 = char + s1
print(s1)

s.reverse()

name = {
    124: "Сергей",
    444: "Анатолий",
    952: "Николай"}
user_id = 375
print(name.get(user_id, "Алексей"))

s = list(map(lambda x: x * x, (1, 2, 3, 4)))
print(s)

import numpy as np
a = np.array([[2, 4],[2, 8]])
print(np.mean(a))

s = list(map(lambda x, y: x + y, [1, 2, 3], [4, 5, 6]))
print(s)

import numpy as np
mtx=np.array([[1, 2],
              [3, 4]])

print(mtx.shape)

import numpy as np
mtx=np.array([[1, 2],
              [3, 4]])

print(mtx.size)