Pythonic way of inserting lines to a file

Question

So as the description describes, I would like to add text to a file in a sequential manner. Say, for example I have a file like this (NOT HTML, this is just an imaginary languag

Answer 1

The most pythonic way for parsing markup is to use a suitable module to parse it.

Answer 2

I would do it like this:

with open(outputfile,'w') as out, open(inputfile) as f:
    for line in f:
        out.write(line)
        if tag_match(line):  #Somehow determine if this line is a match where we want to insert text.
           out.write('\n'.join(fruits)+'\n')

You might come up with a way to make it faster, but I doubt it is worthwhile. This is simple, easy to read, and gets the job done. "pythonic" enough for me :-)