formatting an array and writing into text file

Question

I am new to python and I need a help on formatting an array and storing it in a file.

I have an array say

a = [['C', [0.99813803, -0.00263872, -0.00464602]], ['H', [2.0944175, -0.00242373, 0.00417336]], ['H', [0.63238996, 1.03082951, 0.00417296]], ['H', [0.62561232, -0.52974905, 0.88151021]], ['H', [0.64010219, -0.50924801, -0.90858051]]]

Now I want to store it in a file in the following manner

C   0.99813803 -0.00263872 -0.00464602
H   2.0944175 -0.00242373 0.00417336 
H   0.63238996 1.03082951 0.00417296 
H   0.62561232 -0.52974905 0.88151021
H   0.64010219 -0.50924801 -0.90858051

I tried numpy.savetxt but it stores in array format. I know with, regex I can remove all the special characters, but for me the problem lies only in writing line by line from the array.

Can anyone tell me instead of numpy.savetxt what else I can try ?

Andrés Pérez-Albela H. · Accepted Answer · 2015-11-25 15:15:02Z

1

a = [['C', [0.99813803, -0.00263872, -0.00464602]], ['H', [2.0944175, -0.00242373, 0.00417336]], ['H', [0.63238996, 1.03082951, 0.00417296]], ['H', [0.62561232, -0.52974905, 0.88151021]], ['H', [0.64010219, -0.50924801, -0.90858051]]]

with open('file.txt', 'w') as f:
for item, values in a:
    line = "{}   {} {} {}\n".format(item, *values)
    f.write(line)

File contents (output):

C   0.99813803 -0.00263872 -0.00464602
H   2.0944175 -0.00242373 0.00417336
H   0.63238996 1.03082951 0.00417296
H   0.62561232 -0.52974905 0.88151021
H   0.64010219 -0.50924801 -0.90858051

edited Nov 25, 2015 at 15:15

answered Nov 25, 2015 at 15:05

Andrés Pérez-Albela H.

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8 Comments

ShadowRanger Over a year ago

I'd use unpacking in the loop to simplify a bit, and if the set of values is known to be exactly three elements, always, you could also simplify the format line: for item, values in a:, line = {} {} {} {}\n.format(item, *values) (the final write line is unchanged). Also note: The OP put three spaces between the "line header" and the values.

Vinod Prime Over a year ago

Yeah it's always 3 elements

Andrés Pérez-Albela H. Over a year ago

@ShadowRanger Changed. Thank you! I've learned something today.

Vinod Prime Over a year ago

@AndrésPérez-AlbelaH : just for learning am asking what if my array looks like this [ [['C', [0.99813803, -0.00263872, -0.00464602]], ['H', [2.0944175, -0.00242373, 0.00417336]], ['H', [0.63238996, 1.03082951, 0.00417296]], ['H', [0.62561232, -0.52974905, 0.88151021]], ['H', [0.64010219, -0.50924801, -0.90858051]]]]

ShadowRanger Over a year ago

@VinodPrime: That looks like the same list as in the question, but with an extra layer of brackets around it. You could just do for item, values in a[0]: if it's just a single element list of list of lists. If it's not just a single element, and you want to flatten the outer layer, you'd import itertools then do: for item, values in itertools.chain.from_iterable(a): which would flatten one level of nesting.

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Sede · Accepted Answer · 2015-11-25 15:44:23Z

It seems like you are trying to write a tsv or csv file where delimiter is tab or space. So why not use the csv module

import csv
from itertools import chain

a = [['C', [0.99813803, -0.00263872, -0.00464602]], ['H', [2.0944175, -0.00242373, 0.00417336]], ['H', [0.63238996, 1.03082951, 0.00417296]], ['H', [0.62561232, -0.52974905, 0.88151021]], ['H', [0.64010219, -0.50924801, -0.90858051]]]
with open('filename', 'w') as f:
    writer = csv.writer(f, delimiter='\t', dialect='excel-tab')
    writer.writerows([list(chain.from_iterable(i)) for i in a])

Then your file content look like this:

C    0.99813803    -0.00263872    -0.00464602
H    2.0944175    -0.00242373    0.00417336
H    0.63238996    1.03082951    0.00417296
H    0.62561232    -0.52974905    0.88151021
H    0.64010219    -0.50924801    -0.90858051

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