How to save multiple outputs from a for loop in python to a text file?

Question

I'm trying to save the output of the for loop in a text file along with its corresponding variables. However, when I do the following I only get the last line as an output.

a = [1,2,3,4]
    
b = [4,5,6,7]

c = [5]

file=open("my_output.txt", 'a')

for i, j in zip(a, b):
    z = (i**2)*j+c[0]
    print (z)
    z = str(z)
    
file.write(z + "\n")
file.close()

My output:

What I'm looking for:

a,b,c,z
1,4,5,9
2,5,5,25
3,6,5,59
4,7,5,117

Would appreciate any support. Thank you in advance.

You're only writing to the file outside the loop. What do you expect that does? — Mad Physicist
– Mad Physicist, Commented Sep 3, 2020 at 3:44
if you want to use single value why defining it as a list c = [5]? you can use c= 5 — deadshot
– deadshot, Commented Sep 3, 2020 at 3:46
Did you know print can write to files? Using f-string you can just print to file. See my example below. — Prayson W. Daniel
– Prayson W. Daniel, Commented Sep 3, 2020 at 4:23

Prayson W. Daniel · Accepted Answer · 2020-09-03 04:24:49Z

1

The issue in your code is that you are writing outside your loop and thus getting the last value only. Writing inside the loop will fix it.

There is a simpler way. print can write to files:

# python 3.6+

a = [1,2,3,4]
b = [4,5,6,7]
c = [5]

with open("my_output.txt", 'a+') as f:
    print('a,b,c,z', end='\n', sep=',', file=f)
    for i, j in zip(a, b):
        print(f'{i},{j},{c[0]},{(i**2)*j+c[0]}', end='\n', sep=',', file=f)

edited Sep 3, 2020 at 4:24

answered Sep 3, 2020 at 4:19

Prayson W. Daniel

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1 Comment

personaltest25 Over a year ago

Oh that is way simpler! To be honest I wasn't aware that I can save with print function! Many thanks @ Prayson W. Daniel

Subbu VidyaSekar · Accepted Answer · 2020-09-03 04:00:08Z

0

Code to calculate the z. then write the a,b,c,z into the file.

    a = [1, 2, 3, 4]
    b = [4, 5, 6, 7]
    c = [5]
    zs = []
    col = ['a','b','c','z']
    file = open("my_output.txt", 'a')
    for i, j in zip(a, b):
        z = (i ** 2) * j + c[0]
        print(z)
        zs.append([i,j,c[0],z])
    file.write(str(zs))
    file.close()

edited Sep 3, 2020 at 4:00

answered Sep 3, 2020 at 3:53

Subbu VidyaSekar

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