How can I create a numpy matrix of floats from input?

Question

I'm trying to create a matrix of floats from the user's input.

I've tried this code:

import numpy as np 

m = int(input('Number of lines m: '))

matrix = []
for i in range(m):
   # taking row input from the user
   row = list(map(int, input(f'Line {i} ').split()))
   # appending the 'row' to the 'matrix'
   matrix.append(row)
    
print(matrix)

How can I turn that into a numpy matrix of floats?

Does this answer your question? https://stackoverflow.com/a/26224619/15035314 — Алексей Р, Oct 23 '21 at 23:51

Girardi · Answer 1 · 2021-10-24T06:47:52.093

1

After that, just use

np.array(matrix, dtype=float)

edited Oct 24 '21 at 06:47

answered Oct 23 '21 at 23:08

Girardi

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Thanks for your answer, Girardi! But isn't this going to be a matrix of int numbers? – Patrícia Oct 23 '21 at 23:44
1

You can specify a `dtype` in `np.array(..., dtype=float)` – rafaelc Oct 23 '21 at 23:54

score 0 · Accepted Answer · answered Oct 23 '21 at 23:45

A nice basic input:

In [80]: alist = []
    ...: for _ in range(3):
    ...:     astr=input()
    ...:     alist.append(astr.split())
    ...: arr = np.array(alist, float)
1 2 3
4 5 6
7 8 9
In [81]: alist
Out[81]: [['1', '2', '3'], ['4', '5', '6'], ['7', '8', '9']]
In [82]: arr
Out[82]: 
array([[1., 2., 3.],
       [4., 5., 6.],
       [7., 8., 9.]])

We could enhance it with the ability to set the number of rows, and check that the number of substrings are consistent. But this shows the basic structue.

But for making an array for testing, I prefer to use something like:

In [83]: np.arange(1,10).astype(float).reshape(3,3)
Out[83]: 
array([[1., 2., 3.],
       [4., 5., 6.],
       [7., 8., 9.]])

How can I create a numpy matrix of floats from input?

2 Answers2