writing multiple out files from for loop

Question

out_file = open('result.txt', 'w')
A = [1,2,3,4,5,6,7,8,9,10]
B = [11,12,13,14,15]
for a in A:
    for b in B:
        result = a + b
        print (result, file = out_file)
out_file.close()

The above program writes one out file (result.txt) consisting of all the results (50 elements) together.

I want to write ten out files each consisting of 5 elements and named as follows:

1.txt

2.txt

...

10.txt

The 1.txt file will put the sum of 1+11, 1+12, 1+13, 1+14, and 1+15.

The 2.txt file will put the sum of 2+11, 2+12, 2+13, 2+14, and 2+15.

.....

The 10.txt file will put the sum of 10+11, 10+12, 10+13, 10+14, and 10+15.

Any help, please. Very simple program is expected.

Again, when I wanted to name the out file using elements of N, why I could not?

A = [1,2,3,4,5,6,7,8,9,10]
B = [11,12,13,14,15]
N = ['a','b','c','d','e','f','g','h','i','j']
for a in A:
    results = []
    for b in B:
        result = a + b
        results.append(result)
        for n in N:
            with open('{}.txt'.format(n),'w') as f:
                for res in results:
                    f.write(str(res)+'\n')

if this is a homework and not the real world use-case (that can be useful for someone else except you) you should at least mark it accordingly. Thnx — Yauhen Yakimovich
– Yauhen Yakimovich, Commented Jun 11, 2013 at 10:45
Instead of names like 1.txt, 2.txt this time you want a.txt, b.txt etc, but same content in the files? — Ashwini Chaudhary
– Ashwini Chaudhary, Commented Jun 11, 2013 at 13:03

Ashwini Chaudhary · Accepted Answer · 2013-06-11 13:09:20Z

2

A = [1,2,3,4,5,6,7,8,9,10]
B = [11,12,13,14,15]
for a in A:
    results = []           # define new list for each item in A
    #loop over B and collect the result in a list(results)
    for b in B:
        result = a + b
        results.append(result)   #append the result to results
    #print results               # uncomment this line to see the content of results
    filename = '{}.txt'.format(a)      #generate file name, based on value of `a`
    #always open file using `with` statement as it automatically closes the file for you
    with open( filename , 'w') as f:
       #now loop over results and write them to the file
       for res in results:
          #we can only write a string to a file, so convert numbers to string using `str()`
          f.write(str(res)+'\n') #'\n' adds a new line

Update:

You can use zip() here. zip return items on the same index from the sequences passed to it.

A = [1,2,3,4,5,6,7,8,9,10]
B = [11,12,13,14,15]
N = ['a','b','c','d','e','f','g','h','i','j']
for a,name in zip(A,N):
    results = []
    for b in B:
        result = a + b
        results.append(result)
    filename = '{}.txt'.format(name)
    with open( filename , 'w') as f:
       for res in results:
           f.write(str(res)+'\n')

Help in zip:

>>> print zip.__doc__
zip(seq1 [, seq2 [...]]) -> [(seq1[0], seq2[0] ...), (...)]

Return a list of tuples, where each tuple contains the i-th element
from each of the argument sequences.  The returned list is truncated
in length to the length of the shortest argument sequence.

edited Jun 11, 2013 at 13:09

answered Jun 11, 2013 at 10:41

Ashwini Chaudhary

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12 Comments

lisa Over a year ago

@ Ashwini Chaudhary thank you for quick response. i accepted your answer because it provided the result i was looking for. unfortunately, i could not understand at all. could you please teach me slowly and simply.

Ashwini Chaudhary Over a year ago

@lisa I've added some explanations, let me know which part you didn't understand.

lisa Over a year ago

thank you. i did not catch where did you separate results into ten parts

Ashwini Chaudhary Over a year ago

@lisa I am storing the result in results list for each item in A. i.e after first iteration results list is [12, 13, 14, 15, 16].

Ashwini Chaudhary Over a year ago

@lisa add a print results line before filename line to see what does results contain.

|

John La Rooy · Accepted Answer · 2013-06-11 10:45:34Z

1

A = [1,2,3,4,5,6,7,8,9,10]
B = [11,12,13,14,15]
for a in A:
    with open(str(a) + '.txt', 'w') as fout:
        fout.write('\n'.join(str(a + b) for b in B)

answered Jun 11, 2013 at 10:45

John La Rooy

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1 Comment

John La Rooy Over a year ago

@AshwiniChaudhary, yes I did :/

Martin Maillard · Accepted Answer · 2013-06-11 10:46:46Z

0

A = range(1, 10 + 1)
B = range(11, 15 + 1)

for a in A:
    with open('{}.txt'.format(a), 'wb') as fd:
        for b in B:
            result = a + b
            fd.write('{}\n'.format(result))

answered Jun 11, 2013 at 10:46

Martin Maillard

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