การคำนวณทีละสมาชิก

# Python list approach -- slow
a = [1, 2, 3, 4]
b = [10, 20, 30, 40]
result = [x + y for x, y in zip(a, b)]
print(result)  # [11, 22, 33, 44]

# NumPy approach -- fast
import numpy as np
na, nb = np.array(a), np.array(b)
print(na + nb)  # [11 22 33 44]

import numpy as np

a = np.array([10, 20, 30])
b = np.array([1, 2, 3])

print(a + b)   # [11 22 33]
print(a - b)   # [ 9 18 27]

import numpy as np

a = np.array([10, 20, 30])
b = np.array([2, 4, 5])

print(a * b)    # [ 20  80 150]
print(a / b)    # [5.  5.  6.]
print(a // b)   # [5 5 6]
print(a % b)    # [0 0 0]

import numpy as np

a = np.array([1, 2, 3, 4, 5])

print(a + 10)   # [11 12 13 14 15]
print(a * 2)    # [ 2  4  6  8 10]
print(a ** 2)   # [ 1  4  9 16 25]
print(a / 10)   # [0.1 0.2 0.3 0.4 0.5]

import numpy as np

a = np.array([1.0, 4.0, 9.0, 16.0])
print(a ** 0.5)       # [1. 2. 3. 4.]
print(np.sqrt(a))     # [1. 2. 3. 4.]
print(a ** 2)         # [  1.  16.  81. 256.]

import numpy as np

a = np.array([3, 7, 2, 9, 1])
print(a > 4)    # [False  True False  True False]
print(a == 2)   # [False False  True False False]
print(a >= 3)   # [ True  True False  True False]

import numpy as np

a = np.array([3, 7, 2, 9, 1])
mask = (a > 2) & (a < 8)
print(mask)   # [ True  True False False False]
print(a[mask])  # [3 7]

import numpy as np

a = np.array([1.0, 2.0, 3.0])
a += 10.0
print(a)   # [11. 12. 13.]
a *= 2.0
print(a)   # [22. 24. 26.]

import numpy as np

A = np.array([[1, 2], [3, 4]])
B = np.array([[5, 6], [7, 8]])

print(A + B)
# [[ 6  8]
#  [10 12]]

print(A * B)  # element-wise, NOT matrix multiply
# [[ 5 12]
#  [21 32]]

import numpy as np

a = np.array([1, 2, 3], dtype=np.int32)
b = np.array([0.5, 1.5, 2.5], dtype=np.float64)

c = a + b
print(c)        # [1.5 3.5 5.5]
print(c.dtype)  # float64

import numpy as np

a = np.array([-3, 0, 4, -7, 2])
print(np.abs(a))    # [3 0 4 7 2]
print(np.sign(a))   # [-1  0  1 -1  1]