# -*- coding:utf-8 -*-

# author:

import numpy

'''ndarray的基本索引'''

x = numpy.array([[1,2],[3,4],[5,6]])

print(x[0]) # [1,2]

print(x[0][1]) # 2,普通python数组的索引

print(x[0,1]) # 同x[0][1]，ndarray数组的索引

x = numpy.array([[[1, 2], [3,4]], [[5, 6], [7,8]]])

print(x[0]) # [[1 2],[3 4]]

y = x[0].copy() # 生成一个副本

z = x[0] # 未生成一个副本

print(y) # [[1 2],[3 4]]

print(y[0,0] )# 1

y[0,0] = 0

z[0,0] = -1

print(y )# [[0 2],[3 4]]

print(x[0]) # [[-1 2],[3 4]]

print(z) # [[-1 2],[3 4]]

'''ndarray的切片'''

x = numpy.array([1,2,3,4,5])

print(x[1:3]) # [2,3] 右边开区间

print(x[:3] )# [1,2,3] 左边默认为 0

print(x[1:]) # [2,3,4,5] 右边默认为元素个数

print(x[0:4:2]) # [1,3] 下标递增2

x = numpy.array([[1,2],[3,4],[5,6]])

print(x[:2] )# [[1 2],[3 4]]

print(x[:2,:1] )# [[1],[3]]

x[:2,:1] = 0 # 用标量赋值

print(x )# [[0,2],[0,4],[5,6]]

x[:2,:1] = [[8],[6]] # 用数组赋值

print(x) # [[8,2],[6,4],[5,6]]