Remove lines that contain certain string

user_1512491 0
Viewed 132477

I'm trying to read a text from a text file, read lines, delete lines that contain specific string (in this case 'bad' and 'naughty'). The code I wrote goes like this:

infile = file('./oldfile.txt')

newopen = open('./newfile.txt', 'w')
for line in infile :

    if 'bad' in line:
        line = line.replace('.' , '')
    if 'naughty' in line:
        line = line.replace('.', '')
    else:
        newopen.write(line)

newopen.close()

I wrote like this but it doesn't work out.

One thing important is, if the content of the text was like this:

good baby
bad boy
good boy
normal boy

I don't want the output to have empty lines. so not like:

good baby

good boy
normal boy

but like this:

good baby
good boy
normal boy

What should I edit from my code on the above?

line python
10 Answers

Try this works well.

import re

text = "this is bad!"
text = re.sub(r"(.*?)bad(.*?)$|\n", "", text)
text = re.sub(r"(.*?)naughty(.*?)$|\n", "", text)
print(text)
user_158653590

Regex is a little quicker than the accepted answer (for my 23 MB test file) that I used. But there isn't a lot in it.

import re

bad_words = ['bad', 'naughty']

regex = f"^.*(:{'|'.join(bad_words)}).*\n"
subst = ""

with open('oldfile.txt') as oldfile:
    lines = oldfile.read()

result = re.sub(regex, subst, lines, re.MULTILINE) 

with open('newfile.txt', 'w') as newfile:
    newfile.write(result)

enter image description here

user_20071530 
bad_words = ['doc:', 'strickland:','\n']

with open('linetest.txt') as oldfile, open('linetestnew.txt', 'w') as newfile:
    for line in oldfile:
        if not any(bad_word in line for bad_word in bad_words):
            newfile.write(line)

The \n is a Unicode escape sequence for a newline.

user_124310340
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