Question

After finding a specific line with keyword “banana”, I would like to delete the subsequent line, in this case, “berry”.

Sample.txt

orange
apple
banana
berry
melon

My script, however, deletes “banana” not “berry”….Why?

import fileinput

filename = r"C:\sample.txt"
for linenum,line in enumerate(fileinput.FileInput(filename, inplace=1)):
    if "banana" in line:
        counter = linenum + 1
        if linenum == counter:
            line.strip()
    else:
        print line,

Answer 1

Do it like this:

import fileinput

fin = fileinput.input('/home/jon/text.txt', inplace=1)
for line in fin:
    print line,
    if line.strip() == 'banana':
        next(fin, None) # as suggested by @thg435 doesn't hurt to use default to avoid StopIteration (as next iteration will just be a no-op anyway)

This takes advantage of iterating the fin object so it doesn’t see the next row – meaning you don’t have to worry about setting/unsetting flags… (which can lead to errors)