creating a matrix or a list of lists with python

Question

I working through a tutorial working on lists and using tic-tac-toe.

I am given a string like: XOXOXOXXO

And I'd like to convert this into a matrix or a list of list, for example:

tic_tac_toe= [[ 'X', 'O', 'X'], [ 'O', 'X', 'O'], [ 'O', 'X', 'X']]

I can get this as a 'list', but I can't get this as a list of lists.

I've been searching various posts, and one challenge is I see a lot that are 5 or 7 years old, and I have to wonder how relevant some of the answers still are, and I haven't been able to make work those prior recommendations.

player_actions = 'XO_OOX_X_'

cells = list()

print('Before loop:', player_actions)

for char in player_actions:
    cells.insert(0, ''.join(char.split()))

# Output
print('After loop:', cells)

Output example:
Before loop: XOXOXOXXO
After loop: ['O', 'X', 'X', 'O', 'X', 'O', 'O', 'X', 'X']

Goal: [['O', 'X', 'X'],['O', 'X', 'O'],['O', 'X', 'X']]

Your desired output [['O', 'X', 'X'],['O', 'X', 'O'],['O', 'X', 'X']] doesn't seem to match your input string XOXOXOXXO — Nick
– Nick, Commented Jun 17, 2020 at 1:34
piecing together the above from several runs, and I grabbed the wrong parts for illustration. I apologize for the confusion. — Wolftales
– Wolftales, Commented Jun 17, 2020 at 3:25

DirtyBit · Accepted Answer · 2020-06-17 01:44:34Z

1

Using slicing, create a batch of equally distributed elements:

s = 'XOXOXOXXO'
splitted = [s[x:x+3] for x in range(0,len(s),3)]
print([[i] for i in splitted])

one-liner:

print([[i] for i in [s[x:x+3] for x in range(0,len(s),3)]]) # [['XOX'], ['OXO'], ['XXO']] 
print([[i for i in s[x:x+3]] for x in range(0,len(s),3)])   # [['X', 'O', 'X'], ['O', 'X', 'O'], ['X', 'X', 'O']]

edited Jun 17, 2020 at 1:44

answered Jun 17, 2020 at 1:33

DirtyBit

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1 Comment

Wolftales Over a year ago

I kept trying this with standard for loops but would run into index out of range errors. Thanks for sharing the list comprehension version.

Sarthak Kumar · Accepted Answer · 2020-06-17 01:33:32Z

1

Use numpy array and reshape it after that

code

import numpy as np

arr = ['O','X','O','X','X','O','X','X','O'] #let's take this list as an example

arr = np.array(arr).reshape(3,3) #this creates a 3x3 matrix of the given list

arr = arr.tolist() #if you want to convert numpy array back to list

print(arr)

#output
# [['O', 'X', 'O'], ['X', 'X', 'O'], ['X', 'X', 'O']]

answered Jun 17, 2020 at 1:33

Sarthak Kumar

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2 Comments

Wolftales Over a year ago

I saw the numpy modules mentioned with matrix. I was trying to do this without importing a module, but this works pretty well. Thanks for sharing it.

Sarthak Kumar Over a year ago

@Wolftales Happy to help, just my two cents I thinks it's better to use numpy when dealing with multi dimensional arrays.

Nick · Accepted Answer · 2020-06-17 01:39:14Z

1

Assuming your actual desired output for

player_actions = 'XOXOXOXXO'

is

[['X', 'O', 'X'], ['O', 'X', 'O'], ['X', 'X', 'O']]

you can generate that using a nested list comprehension:

cells = [[c for c in player_actions[i:i+3]] for i in range(0, len(player_actions), 3)]

answered Jun 17, 2020 at 1:39

Nick

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1 Comment

Wolftales Over a year ago

This was my intent. Thank you.

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