[Tutor] Appending an extra column in a data file

[Albert-Jan Roskam]

> Subject: Re: [Tutor] Appending an extra column in a data file
> 
<snip>
 
> The file you attached is a space-delimited text file. If you want to
> add a third column with the value '1.0' on every row you can just do:
> 
> with open('old.dat') as fin, open('new.dat', 'w') as 
> fout:
>     for line in fin:
>         fout.write(line[:-1] + ' 1.0\n')

Is that Python 3.x? I thought this "double context manager" could only be done with contextlib.nested, e.g.:
>>> with contextlib.nested(open(fn, "rb"), open(fn[:-4] + "_out.dat", "wb")) as (r, w):
...     for inline in r:
...             w.write(inline + " " + "somevalue" + "\n")

Your code looks cleaner though.

Regards,
Albert-Jan