Converting a .dat file into an array

Question

I have a .dat file generated from MATLAB (with float values). I need to convert it to an array containing the same number of rows and columns as it did in the .dat file. Could anyone suggest a way of doing this? There is a \n at the end of each line which I want to remove. The .dat file read into Python looks like this:

12,18\n42,17\n60,16\n86,17\n120,17\n137,12\n169,10\n189,14\n215,9\n248,11\n273,12\n301,17\n319,8\n345,17\n378,14\n403,10\n423,10\n453,18\n483,10\n507,15\n10,43\n43,44\n60,38\n96,41\n114,41\n139,41\n168,43\n189,40\n215,37\n248,45\n268,45\n301,37\n321,35\n

And I would like the output to be in the following format:

12,18
42,17
...

where 12,42 and 18,17 are in different columns.

Can you give some sample data? Will the number of columns differ for each row? — 18bytes
– 18bytes, Commented Jun 28, 2012 at 14:45
Presumably this is a follow up question to your previous question. If you found answers to this previous question helpful then don't forget to upvote those helpful answers and accept one of them. — Chris
– Chris, Commented Jun 28, 2012 at 15:11
@Chris: Care to explain why you changed 12,18 to 12, 18 in the output format description ? That's not the same thing. — lqc
– lqc, Commented Jun 28, 2012 at 15:17
@lqc It was an assumption on my part that the data was made up of two columns of data. I noticed that your comment suggests , is a decimal place (it's not here in the UK) so I have rolled back the changes. @user1482980 can you clarify this point at all? — Chris
– Chris, Commented Jun 28, 2012 at 15:19

mgilson · Accepted Answer · 2012-06-28 15:06:30Z

1

what do you mean by array?

with open('datafile','r') as f:
    rows=[map(float,L.strip().split(',')) for L in f]  # list of lists

arr=np.array(rows)  #Numpy array (assuming you `import numpy as np`)

Or using numpy.loadtxt:

arr=np.loadtxt('datafilename',delimiter=',')

edited Jun 28, 2012 at 15:06

answered Jun 28, 2012 at 14:46

mgilson

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7 Comments

user1482980 Over a year ago

@devsundar: I've edited the post and given the sample data and the output format.

user1482980 Over a year ago

:i have an additional \n character due to which hte above code u suggested gives an error(ValueError: invalid literal for float(): 12,18)

jfs Over a year ago

call loadtxt() if you use numpy

mgilson Over a year ago

Downvoter : Care to elaborate (Or at least post an alternative so the user isn't left wondering what (s)he should do since this is apparently a bad way to do it)?

mgilson Over a year ago

@lqc -- I'm aware of that (although I don't think about it often). Anyway, in this case, it's obvious that the ',' is being used as a field separator. He chose to store the data in a csv file, not me ;-)

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