Extracting rows/columns of numbers from a txt file in Python

Question

I am fairly new to Python and have encountered a small but (what seems to be a) very difficult problem.

I have a txt file which contains the following:

-2 2.1 -0.365635756 0 2.4 0.347433737 2 2.5 0.263774619 4 3.5 -0.244930974 6 4.2 -0.004564913

My aim is to somehow extract separate rows/columns from the file in Python to use as lists or arrays (again, I'm fairly new to this). So for example, how would I make the list [-2, 0, 2, 4, 6] using the data from the first column?

I currently have the following code in my work:

import numpy as np with open('Numbers.txt', 'r') as f: fcontents = f.read() print(fcontents) x = np.array(fcontents)

The objective of this is to write a program that uses arrays to calculate different variables given in our project instructions.

Use the space character as a delimiter in every line of the text file — Jeru Luke
– Jeru Luke, Commented Apr 19, 2017 at 20:21
Possible duplicate of How to Convert a Text File into a List in Python — Barney
– Barney, Commented Apr 19, 2017 at 20:37

Robᵩ · Accepted Answer · 2017-04-19 20:58:15Z

This might be a job for pandas:

import pandas as pd df = pd.read_fwf('Numbers.txt', header=None) first_col = df[0] assert first_col.mean() == 2 assert first_col.median() == 2 assert sum(first_col) == 10

References:

Yay! Pandas rules! But for this particular file format i'd use pd.read_fwf()

davidejones · Accepted Answer · 2017-04-19 20:26:09Z

I haven't used numpy but if you want to separate into columns you can do this kind of thing

col1 = [] col2 = [] col3 = [] with open('Numbers.txt', 'r') as f: for line in f: first, second, third = line.split() col1.append(first) col2.append(second) col3.append(third) print(col1) print(col2) print(col3)

which outputs

['-2', '0', '2', '4', '6'] ['2.1', '2.4', '2.5', '3.5', '4.2'] ['-0.365635756', '0.347433737', '0.263774619', '-0.244930974', '-0.004564913']

Luchko · Accepted Answer · 2017-04-19 21:16:15Z

You can import your data as a numpy.array

import numpy as np data = np.genfromtxt('Numbers.txt', unpack=True).T

Then, retrieving columns/rows is as simple as indexing/slicing a numpy.array

print(data[1,:]) print(data[:,1])

this will results in

[ 0. 2.4 0.34743374] [ 2.1 2.4 2.5 3.5 4.2]

Collectives™ on Stack Overflow

Extracting rows/columns of numbers from a txt file in Python

3 Answers 3

1 Comment

Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Linked

Related