Python - write txt file with a list

Question

I have a test.txt that contains:

-
anything1
go
-
anything2
go

And i wanna replace the '-' with my list and some query. Here is my code:

x = ['1', '2']
i=0
with open("test.txt", "r") as fin:
    with open("result.txt", "w") as fout:
        for line in fin:
            fout.write(line.replace('-','\nuse '+(str(x[i]))+'\ngo\n'))
            i+=i

But my result is:

use 1
go
anything1 
go

use 1
go
anything2 
go

I need that the second 'use' be 'use 2' and not 'use 1'.

How I can fix this?

Thanks

Consider what i+=i does when i is zero. (posting this as a comment and not an answer because fixing this typo won't completely solve your problem) — Kevin
– Kevin, Commented Dec 14, 2017 at 13:44
You need some way to tell your replacing script that the n'th occurrence of "-" translates to the n-1 index in x and just replace the occurrence with the value it finds on x[n-1]. A simple counter should do if you match occurrences to list indexes. — BoboDarph
– BoboDarph, Commented Dec 14, 2017 at 13:46

Ma0 · Accepted Answer · 2017-12-14 13:59:45Z

1

Try this instead:

i = (x for x in ['1', '2'])

with open("test.txt") as fin, open("result.txt", "w") as fout:
    for line in fin:
        if line.startswith('-'):
            fout.write(line.replace('-', '\nuse {}\ngo\n'.format(next(i))))
        else:
            fout.write(line)

edited Dec 14, 2017 at 13:59

answered Dec 14, 2017 at 13:45

Ma0

15.2k4 gold badges38 silver badges70 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

BoboDarph Over a year ago

I think it would be best to do fout.write(line.replace('-', '\nuse {}\ngo\n'.format(str(x[i-1])))), he may want the value from x.

Anonta Over a year ago

You can open the files with one with block: with open("test.txt", "r") as fin, open("result.txt", "w") as fout:

Ma0 Over a year ago

Like it better now?

erhesto Over a year ago

I'd use f'\nuse {next(i)}\ngo\n' as this super fancy feature of Python 3.6 makes code more beautiful (IMO), but your solution works with every version of modern Python, so it's probably better. But I think that it's worth to say, that both original code and yours would throw some exceptions in case if count of '-' characters in file and your generator/list would have different length (there would be more '-' chars than items in generator).

Ma0 Over a year ago

@erhesto next() also takes default arguments. So one could write next(i, 'NaN') for example for bulletproofing. As long as there are is you would get those and when you run out, it will just give 'NaN'

|

Collectives™ on Stack Overflow

Python - write txt file with a list

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related