如何在Python中定义二维数组 [英] How to define a two-dimensional array in Python

问题描述

我想定义一个二维数组，而没有这样的初始化长度:

I want to define a two-dimensional array without an initialized length like this:

Matrix = [][]

但是它不起作用...

but it does not work...

我已经尝试过下面的代码，但这也是错误的:

I've tried the code below, but it is wrong too:

Matrix = [5][5]

错误:

Error:

Traceback ...

IndexError: list index out of range

我怎么了?

推荐答案

从技术上讲，您正在尝试索引未初始化的数组.您必须先使用列表初始化外部列表，然后再添加项目. Python将其称为 列表理解".

You're technically trying to index an uninitialized array. You have to first initialize the outer list with lists before adding items; Python calls this "list comprehension".

# Creates a list containing 5 lists, each of 8 items, all set to 0
w, h = 8, 5;
Matrix = [[0 for x in range(w)] for y in range(h)] 

您现在可以将项目添加到列表:

Matrix[0][0] = 1
Matrix[6][0] = 3 # error! range... 
Matrix[0][6] = 3 # valid

请注意，矩阵是"y"地址主地址，换句话说，"y索引"位于"x索引"之前.

Note that the matrix is "y" address major, in other words, the "y index" comes before the "x index".

print Matrix[0][0] # prints 1
x, y = 0, 6 
print Matrix[x][y] # prints 3; be careful with indexing! 

尽管您可以根据需要命名它们，但如果您对内部列表和外部列表都使用"x"，并且希望使用非平方矩阵，那么我会以这种方式来避免索引可能引起的混淆

Although you can name them as you wish, I look at it this way to avoid some confusion that could arise with the indexing, if you use "x" for both the inner and outer lists, and want a non-square Matrix.

这篇关于如何在Python中定义二维数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！