Read specific lines from text file as numpy array

Question

I am trying to read a txt file in he format:

[text]
[text]
[text]
1 0 
4 5
3 0 0
[text]
.
.
.

I need to read lines 4 to 6 as a numpy array. So far I've got:

 lines=[]
 with open('filename', "r") as f:
     for i, line in enumerate(f):
         if i>=3 and i<=5:
             lines.append(line)
 lines = np.array(lines)

This reads each of the required lines as an element, but I need to have numbers in separate columns as separate elements. Is there a way around this?

Thanks

But then I can't set it as a numpy array. Comes up with error: "setting an array element with a sequence" — Afzal, Oct 06 '15 at 12:27
Your last number line has 3 numbers, the others 2? Do you really want that? — hpaulj, Oct 06 '15 at 16:01

score 2 · Answer 1 · answered Oct 06 '15 at 15:22

You need to transform string to ints:

lines=[]
with open('filename', "r") as f:
    for i, line in enumerate(x.split('\n')):
        if i>=3 and i<=5:
            lines.append([int(y) for y in line.split()])

lines = np.array(lines)
print type(lines)

score 2 · Answer 2 · answered Oct 06 '15 at 16:24

2

You can use itertools.islice() to select the lines and feed that result to Numpy's genfromtxt() function:

from itertools import islice
import numpy as np

with open('test.txt') as lines:
    array = np.genfromtxt(islice(lines, 3, 6))

print array

answered Oct 06 '15 at 16:24

BlackJack

4,476
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score 0 · Answer 3 · answered Jul 01 '22 at 19:30

0

You can do this using skiprows and max_rows in numpy.

array = np.loadtxt(filename,skiprows=3,max_rows=3)

max_rows: number of rows you want to read afters skipping skiprows initial rows.

answered Jul 01 '22 at 19:30

Niladri Gomes

213
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Read specific lines from text file as numpy array

3 Answers3

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