Pythonic way to create a 2d array? [duplicate]

Question

I want to create a 2d array of integer values initially set to 0.

This is how I would think to do it:

grid = [[0] * width] * height

But this just creates each row as a reference to the original, so doing something like

grid[0][1] = 1

will modify all of the grid[n][1] values.

This is my solution:

grid = [[0 for x in range(width)] for y in range(height)]

It feels wrong, is there a better more pythonic way to do this?

EDIT: Bonus question, if the grid size is never going to change and will only contain integers should I use something like a tuple or array.array instead?

Community · Accepted Answer · 2017-05-23 11:53:55Z

4

Since numbers are immutable, using * to create a list should be fine. So, the 2D list initialization can be done like this

[[0] * width for y in range(height)]

edited May 23, 2017 at 11:53

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answered Mar 4, 2014 at 15:24

thefourtheye

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2 Comments

zeffii Over a year ago

why not: [[0]*width]*height

thefourtheye Over a year ago

@zeffii That will create only one list [0]*width] (think of this as l1) and create a list with height elements in which, all of them are the references to l1. So, changing any list will reflect on all the other lists as well.

theaembee · Accepted Answer · 2014-03-04 15:39:46Z

1

You could use numpy.zeros:

import numpy as np
numpy.zeros(height, width)

If it has to be integer use as option dtype=numpy.int8

answered Mar 4, 2014 at 15:39

theaembee

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1 Comment

Igglyboo Over a year ago

Yea I've done it with numpy before but I'm trying to avoid external dependencies for my current project.

user2874724 · Accepted Answer · 2014-03-04 15:51:11Z

0

Here is what I used.

def generate_board(n): #Randomly creates a list with n lists in it, and n random numbers
                       #in each mini list
    list = []
    for i in range(0, n):
        list.append([])
        for j in range(0, n):
            list[i].append(random.randint(0, 9))
    return list

def print_board(board):
    n = len(board) - 1
    while n > -1:
        print str(board[n]) + ' = ' + str(n)
        n -= 1

answered Mar 4, 2014 at 15:51

user2874724

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