Numpy Basics

转载：
https://morvanzhou.github.io/tutorials/data-manipulation/np-pd/

Numpy属性：

• ndim维度
• shape行数和列数
• size元素个数

import numpy as np

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

print('number of dim:',array.ndim)  # 维度
# number of dim: 2

print('shape :',array.shape)    # 行数和列数
# shape : (2, 3)

print('size:',array.size)   # 元素个数
# size: 6

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Numpy创建array

a = np.array([2,23,4])  # list 1d
print(a)
# [2 23 4]

a = np.array([2,23,4],dtype=np.int)
print(a.dtype)
# int 64

np.arrange()

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Numpy基本运算

np.dot()
sum()
min()
max()
argmin()
argmax()
mean()
average()
median()
cumsum()
diff()
nonzero()
sort()
clip()
transpose()

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Numpy索引

A[2]
A[1][1]
A[1,1]
A[1,1:3]
A.flatten

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Numpy array合并
np.vstack()
np.hstack()
np.newaxis()
np.concatenate()

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Numpy array分割

np.split(A, 2, axis=1)
np.split(A, 3, axis=0)

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Numpy copy & deep copy