파이썬 numpy Accessing, Deleting, and Inserting Elements Into ndarrays

Accessing, Deleting, and Inserting Elements Into ndarrays

x = np.random.randint(1, 20, 7)
# array([ 3,  6,  3,  5, 13,  9, 19])

x[3]
# 5

x[-1]
# 19

다차원배열의 인덱스 접근

X = np.random.randint(0, 100, (5, 5))
# array([[39, 48, 91,  8,  8],
#        [12,  7, 70, 25, 69],
#        [54, 77, 71, 92, 73],
#        [12, 20, 39, 45, 53],
#        [ 1, 57, 95, 31, 87]])

X[0,2]
# 91

항목 삭제

x = np.array([ 3,  6,  3,  5, 13,  9, 19])
np.delete(x, 3)
# array([ 3,  6,  3, 13,  9, 19])

X = np.array([[69, 10, 98, 68, 32],
              [14, 56, 73, 48, 69],
              [36, 48, 40, 28, 90],
              [45, 47, 65, 12, 95]])

np.delete(X, 2, axis = 0)
# array([[69, 10, 98, 68, 32],
#        [14, 56, 73, 48, 69],
#        [45, 47, 65, 12, 95]])

np.delete(X, 1, axis = 1)
# array([[69, 98, 68, 32],
#        [14, 73, 48, 69],
#        [36, 40, 28, 90],
#        [45, 65, 12, 95]])

항목을 끝에 추가하기

a = np.arange(5)
a = a.reshape(1, 5)

np.append(X, a, axis = 0)
# array([[69, 10, 98, 68, 32],
#        [14, 56, 73, 48, 69],
#        [36, 48, 40, 28, 90],
#        [45, 47, 65, 12, 95],
#        [ 0,  1,  2,  3,  4]])

b = np.arange(4)
b = b.reshape(4, 1)

np.append(X, b, axis = 1)
# array([[69, 10, 98, 68, 32,  0],
#        [14, 56, 73, 48, 69,  1],
#        [36, 48, 40, 28, 90,  2],
#        [45, 47, 65, 12, 95,  3]])

항목을 원하는 위치에 추가하기

np.insert(X, 1, a, axis = 0)
# array([[69, 10, 98, 68, 32],
#        [ 0,  1,  2,  3,  4],
#        [14, 56, 73, 48, 69],
#        [36, 48, 40, 28, 90],
#        [45, 47, 65, 12, 95]])

np.insert(X, 1, b, axis=1)
# array([[69,  0, 10, 98, 68, 32],
#        [14,  1, 56, 73, 48, 69],
#        [36,  2, 48, 40, 28, 90],
#        [45,  3, 47, 65, 12, 95]])