Python：Numpy學習

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 1 import numpy as np 2 # 基礎屬性 3 array = np.array([[[1,2,3], [0,0,1]], [[1,2,3], [0,0,1]]], 4                  dtype = np.int64) 5  6 print(array) 7 print(array.ndim)  # number of dim 8 print(array.shape) # shape 9 print(array.size)  # number of elements10 print(array.dtype)11 12 # 建立array13 a = np.array([1,2,3,4]) # 1 dim14 15 b = np.array([[1,2,3,4]]) # row vector, 2 dim16 c = np.array([[1], [2], [3] ,[4]]) # column vector, 2 dim17 print(a.shape, b.shape, c.shape)18 19 a = np.zeros( (2,3), dtype = np.float) 20 a = np.ones( (2,3), dtype = np.float)21 a = np.empty( (2,3), dtype = np.float)22 a = np.arange(10, 20) # alike function range23 a = np.linspace(1, 10, 5) # interval 24 print(a)25 26 # 基礎運算（向量式運算）27 ‘‘‘向量‘‘‘28 a = np.array([10, 20, 30, 40])29 b = np.arange(4)30 print( a + b) 31 print( a**2) 32 print( a < 20) 33 34 ‘‘‘矩陣‘‘‘35 a = np.array([[1,1],36               [0,1]])37 b = np.arange(4).reshape((2,2))38 print( a*b )39 print( np.dot(a, b) ) # equal a.dot(b)40 41 print(np.argmax(a)) 42 print(np.argmin(a)) 43 44 A = np.arange(14, 2, -1).reshape((3,4))45 print(np.clip(A, 5, 9))46 47 ‘‘‘隨機數‘‘‘ # module: np.random48 a = np.random.random((2,4))49 print(a)50 print(np.sum(a, axis = 1))51 print(np.min(a, axis = 0))52 53 # 索引54 ‘‘‘一維array‘‘‘55 A = np.arange(3, 15)56 print(A[2])57 print(A[0:5:2])58 59 ‘‘‘二維array‘‘‘60 A = np.arange(3, 15).reshape(3, 4)61 print(A[2])62 print(A[2,:])63 64 print(A[2][1])65 print(A[2, 1])66 67 # array合并68 A = np.array([1,1,1])69 B = np.array([2,2,2])70 71 print(np.vstack((A,B))) # vertival stack72 print(np.hstack((A,B))) # horizontal stack73 74 A[np.newaxis, :] # 1 * 375 A[:, np.newaxis] # 3 * 176 77 a = np.array([[1, 2], [3, 4]])78 b = np.array([[5, 6]])79 80 # array分割81 A = np.arange(12).reshape((3,4))82 83 print(np.split(A, 2, axis = 1))84 print(np.array_split(A, 3, axis = 1))85 print(np.split(A, 3, axis = 0))86 87 print(np.vsplit(A, 3))88 print(np.hsplit(A, 2))89 90 # copy and deep copy91 a = np.array([1,2,3,10])92 b = a93 c = a94 d = b95 96 b = a.copy()97 a[3] = 4498 print(a)99 print(b)

 

Python：Numpy學習