python - Filter lines from a text file which contain a particular word

Question

I want to write a program which filters the lines from my text file which contain the word "apple" and write those lines into a new text file.

What I have tried just writes the word "apple" in my new text file, whereas I want whole lines.

Answer 1

Use can get all lines containing 'apple' using a list-comprehension:

[ line for line in open('textfile') if 'apple' in line]

So - also in one code-line - you can create the new textfile:

open('newfile','w').writelines([ line for line in open('textfile') if 'apple' in line])

And eyquem is right: it's definitely faster to keep it as an iterator and write

open('newfile','w').writelines(line for line in open('textfile') if 'apple' in line)