representing list of tuples as 2d array in python

Question

Say I have a list of tuples containing the RGB information of each pixels in an image from left to right, top to bottom.

[(1,2,3),(2,3,4),(1,2,4),(9,2,1),(1,1,1),(3,4,5)]

Assuming the width and height of the image is already know, is there a way I can represent the image using list of list?

For example, let's say the above list of tuples represent a 2x3 image, image[1][2] should give me the RGB tuple (3,4,5).

image[x][y] => input_list[x * width + y]. [1][2] becomes [1 * 3 + 2]. — Martijn Pieters
– Martijn Pieters, Commented Feb 18, 2014 at 16:40
So what you're really asking is how to convert a 1d list to a 2d list. — 2rs2ts
– 2rs2ts, Commented Feb 18, 2014 at 16:48

2rs2ts · Accepted Answer · 2014-02-18 16:51:50Z

2

Use the step argument in range (or xrange):

>>> width = 2
>>> pixels = [(1,2,3),(2,3,4),(1,2,4),(9,2,1),(1,1,1),(3,4,5)]
>>> image = [pixels[x:x+width] for x in range(0,len(pixels),width)]
>>> image
[[(1, 2, 3), (2, 3, 4)], [(1, 2, 4), (9, 2, 1)], [(1, 1, 1), (3, 4, 5)]]

It will make x increment by the value of the step, instead of the default, which is 1. If you are familiar with Java, it's similar to:

for (int x=0; x<length; x = x+step)

edited Feb 18, 2014 at 16:51

answered Feb 18, 2014 at 16:46

2rs2ts

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