How to create a matrix from a given list without using Numpy in Python

Question

I checked the solution in Creating a Matrix in Python without numpy but this only address square matrixes. That is 3x3 or 4x4.

For example, I tried the answer in those questions with the following lines and it gives list index out of range error.

random_list = random.sample(range(10,99), 10)
print(len(random_list))
mat = createMatrix(5,2,random_list)
print (mat)

My question is given a list with numbers, how to put it into a matrix.

e.g.

column = input("No of Column: ")
rows = input("No of Rows: ")
randomDataList = random.sample(range(10,99), int(column)* int(rows))
createMatrix(int(column), int(rows), randomDataList)

The first answer in that question would seem to work perfectly well for non-square matrices. — Nathan Pierson
– Nathan Pierson, Commented Aug 15, 2020 at 5:40
Oh, yes, it looks like there's a bug. I commented on the original question, but repeating it here: Changing rowCount to colCount in the innermost portion of createMatrix's for loop should fix it. — Nathan Pierson
– Nathan Pierson, Commented Aug 15, 2020 at 5:52

mathfux · Accepted Answer · 2020-08-15 05:47:28Z

1

Another way of list comprehension:

import random
column = input("No of Column: ")
rows = input("No of Rows: ")
n, m = int(rows), int(column)
randomDataList = random.sample(range(10,99), n*m)
print([[randomDataList[i+m*j] for i in range(m)] for j in range(n)])

answered Aug 15, 2020 at 5:47

mathfux

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1 Comment

Akshay Sehgal Over a year ago

2 nested for loops too much of a stretch?

Akshay Sehgal · Accepted Answer · 2020-08-15 05:51:58Z

0

You can use a list comprehension to build a list of lists -

import random

r, c = 4, 5

l = random.sample(range(-10,10),r*c)

matrix = [l[i:i + int(r*c / c)] for i in range(0, len(l), int(r*c / c))]
print(matrix)

[[-10, -4, 7, 4], [1, 9, -5, 6], [-8, 5, 3, -9], [-2, 2, 8, -7], [0, -6, -1, -3]]

edited Aug 15, 2020 at 5:51

answered Aug 15, 2020 at 5:41

Akshay Sehgal

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5 Comments

Archibald Over a year ago

Cannot use Numpy

Akshay Sehgal Over a year ago

Numpy has not been used for the solution. Only to generate the random input list that has to be converted to a 'matrix'

Mario Ishac Over a year ago

np.random.random, unlike random.sample, does not return unique numbers here.

Archibald Over a year ago

My bad. Yes, got it.

Akshay Sehgal Over a year ago

Updated my solution just because. @MarioIshac - So?

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