Importing large set of numbers from a text file into python program in matrix form

Question

I'm trying to import some pointcloud coordinates into python, the values are in a text file in this format

0.0054216 0.11349 0.040749   
-0.0017447 0.11425 0.041273  
-0.010661 0.11338 0.040916  
0.026422 0.11499 0.032623

and so on.
Ive tried doing it by 2 methods

def getValue(filename):       
    try:                                                                            
        file = open(filename,'r')  
    except: IOError:  
       print ('problem with file'), filename       
    value = []  
    for line in file:  
        value.append(float(line))  
    return value

I called the above code in idle but there is an error that says the string cannot be converted to float.

import numpy as np  
import matplotlib.pyplot as plt

data = np.genformtxt('co.txt', delimiter=',')

In this method when I call for data in idle it says data is not defined.

Below is the error message

>>> data[0:4]
Traceback (most recent call last):
File "<pyshell#14>", line 1, in <module>
data[0:4]
NameError: name 'data' is not defined

Can you please format your question and code. Don't use numbers when formatting code as this will mess it up. Please also make sure all code indentation is exactly as it is on your machine — DavidG, Jan 31 '18 at 10:59
If you are getting "data is not defined" error then this has nothing to do with reading a file. You need to create a [Minimal, Complete, and Verifiable Example](http://stackoverflow.com/help/mcve). — DavidG, Jan 31 '18 at 11:08
Im sorry to ask this question, but before executing `data[0:4]`, have you executed `data = np.genformtxt('co.txt', delimiter=',')`. Because it seems that your variable hasn't been created. — Ivan, Jan 31 '18 at 14:34
It is working now when i put the path for 'co.txt', although i don't understand why it said data is not defined — Sarvesh Kumar Malladi, Feb 01 '18 at 04:29

score 0 · Answer 1 · answered Jan 31 '18 at 11:02

0

With the data you provided I would say you are trying to use:

np.loadtxt(<yourtxt.txt>, delimiter=" ")

In this case your delimiter should be blank space as can be seen in you data. This works perfectly for me.

Your problem is you are using the comma as delimiter.

answered Jan 31 '18 at 11:02

Ivan

782
11
23

Ive tried using space as well but the error does not seem to be because of this, the error says the name data is not defined – Sarvesh Kumar Malladi Jan 31 '18 at 11:07
Using your same method (`genfromtxt`) works for me if I put delimiter as blank space... – Ivan Jan 31 '18 at 11:12
Im sorry, but with the things you provided cant help you more, its working for me with the space... Good luck – Ivan Jan 31 '18 at 11:18
@SarveshKumarMalladi The error has nothing to do with reading the data. You need to provide a [MCVE](https://stackoverflow.com/help/mcve) – DavidG Jan 31 '18 at 11:19
Sorry Im trying to add the error message Im still not comfortable with the formating, please bear with it – Sarvesh Kumar Malladi Jan 31 '18 at 11:24

score 0 · Answer 2 · answered Jan 31 '18 at 18:20

float() converts one number string, not several (read its docs)

In [32]: line = '0.0054216 0.11349 0.040749 '
In [33]: float(line)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-33-0f93140abeab> in <module>()
----> 1 float(line)

ValueError: could not convert string to float: '0.0054216 0.11349 0.040749 '

Note that the error tells us which string is giving it problems.

It works if we split the line into substrings and convert those individually.

In [34]: [float(x) for x in line.split()]
Out[34]: [0.0054216, 0.11349, 0.040749]

Similarly, genfromtxt needs to split the lines into proper substrings. There aren't any , in your file, so clearly that's the wrong delimiter. The default delimiter is white space, which works just fine in this case.

In [35]: data = np.genfromtxt([line])
In [36]: data
Out[36]: array([0.0054216, 0.11349  , 0.040749 ])

With the wrong delimiter it tries to convert the whole line to a float. It can't (same reason as above), so it uses np.nan instead.

In [37]: data = np.genfromtxt([line], delimiter=',')
In [38]: data
Out[38]: array(nan)

I tried out what you suggested but it just tells me problem with file — Sarvesh Kumar Malladi, Feb 01 '18 at 04:50

Importing large set of numbers from a text file into python program in matrix form

2 Answers2