第1篇 numpy 语法

import numpy as np
A = np.array([
    [1, 2, 3, 4],
    [5, 6, 7, 8],
], dtype=int)  # dtype指定数据类型int float
print(A)
print(A.size)  # 元素的总个数
print(A.ndim)  # 维度
print(A.shape)  # 形状 (2, 4)  小元组 两行四列

B = np.zeros((2, 3))  # 0矩阵
C = np.ones((3, 4))  # 1矩阵
D = np.empty((3, 2))  # 空矩阵
print(B)
print(C)
print(D)

E = np.arange(9).reshape((3, 3))
print(E)
"""
[[0 1 2]
 [3 4 5]
 [6 7 8]]
"""

F = np.linspace(0, 10, 5)  # [ 0.   2.5  5.   7.5 10. ]
print(F)
G = np.linspace(0 ,10, 6).reshape((2, 3))
print(G)
"""
[[ 0.  2.  4.]
 [ 6.  8. 10.]]
"""

# 数学运算
H = np.array([
    [1, 2],
    [3, 4],
])
print(np.sin(H))
"""
[[ 0.84147098  0.90929743]
 [ 0.14112001 -0.7568025 ]]

"""
print(H < 3)
"""
[[ True  True]
 [False False]]
"""

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

G = np.array([
    [1, 0],
    [0, 1],
])
print(H*G)
"""
[[1 0]
 [0 4]]
"""
print(np.dot(H,G))
"""
[[1 2]
 [3 4]]

"""

H = np.random.random((2,4))
print(H)
"""
[[0.60344911 0.08797164 0.24912686 0.14263465]
 [0.36800238 0.45952787 0.26052571 0.80598184]]
"""
print(np.sum(H))  # 所有元素相加
print(np.max(H))  # 元素中最大的
print(np.min(H))  # 元素中最小的

J = np.arange(9).reshape((3, 3))
print(J)
"""
[[0 1 2]
 [3 4 5]
 [6 7 8]]
"""
print(J.argmax())  # 8
print(J.argmin())  # 0
print(J.mean())  # 4
print(J.cumsum())  # [ 0  1  3  6 10 15 21 28 36]
print(np.diff(J))
"""
[[1 1]
 [1 1]
 [1 1]]
"""

K = np.arange(14,2,-1).reshape((3,4))
print(K)
"""
[[14 13 12 11]
 [10  9  8  7]
 [ 6  5  4  3]]
"""
print(np.sort(K))
"""
[[11 12 13 14]
 [ 7  8  9 10]
 [ 3  4  5  6]]
"""

# 转置
K = np.arange(14,2,-1).reshape((3,4))
print(K)
# print(np.transpose(K))
print(K.T)
print(np.dot(K.T,K))  # K**2
print((K.T).dot(K))
"""
[[332 302 272 242]
 [302 275 248 221]
 [272 248 224 200]
 [242 221 200 179]]
"""
print(np.clip(K, 5, 9))  # 截取5--9之间
"""
[[9 9 9 9]
 [9 9 8 7]
 [6 5 5 5]]
"""
print(K)
"""
[[14 13 12 11]
 [10  9  8  7]
 [ 6  5  4  3]]
"""
print(np.mean(K, axis=1))
"""
[12.5  8.5  4.5]
"""
print(np.mean(K, axis=0))
"""
[10.  9.  8.  7.]
"""