python: rows from a textfile

Question

I want to save the whole output of test.py in an array. How can I do this?

test.txt

1.0  0.0  3.0
2.0  0.5  0.0

6.0  4.0  2.0
1.0  0.0  3.0

test.py

a = [0,1]

with open('test.txt') as fd:
    for n, line in enumerate(fd):
        if n in a:
            t = numpy.array(line.split())
            print(t)

Output:

['1.0' '0.0' '3.0']
['2.0' '0.5' '0.0']

print beyond the loop:

print(t)

Output beyond the loop:

['2.0' '0.5' '0.0']

How can I get something like this?

[['1.0' '0.0' '3.0']
['2.0' '0.5' '0.0']]

So you only want to read the first two lines and save them as a list of lists? — ywbaek, Mar 31 '20 at 13:41
no I wanted to read the first two lines and save it as an array. I want to get a matrix 2x3 out of them — Jolosin, Mar 31 '20 at 13:45
Python doesn't have a built-in array type. You can use `array` or `numpy` modules. If you want to use a list then you can create an empty list and append each line. — ywbaek, Mar 31 '20 at 13:48

score 0 · Accepted Answer · answered Mar 31 '20 at 13:52

If you don't know the size ahead of time, you can append to a list instead, then convert to numpy array.

import numpy as np
a = [0,1]
d = []
with open('test.txt') as fd:
    for n, line in enumerate(fd):
        if n in a:
            d.append(line.split())

np.asarray(d)

score 0 · Answer 2 · edited Mar 31 '20 at 14:31

0

The answer for your question is published in the following post: How to read a file line-by-line into a list?

Summing up the solution from @SilentGhost for your code:

with open('test.txt') as fd:
    t = fd.readlines()
t = [x.strip() for x in t]

edited Mar 31 '20 at 14:31

Dharman

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answered Mar 31 '20 at 13:53

GiulioSanto

70
5

He wants to store his in-memory list to a file in a format similar to array. – abhiarora Mar 31 '20 at 13:54

python: rows from a textfile

2 Answers2