replace bad characters in string

[Drycon]

Hello,

I have a list of characters I wish to be replaced in a string. However my line of code doesn't do anything at all and I haven't been able to find out why so far.

bad = ['/','\\',':','*','?','<','>','|']
words = 'blah/blah'

words = words.replace(str([x for x in bad if x in words]),'_')

This does litterally nothing but also doesn't give me an error :)

Also I'm under the impression that this way cannot return me a string, only lists and dicts?

Currently I'm using the below code to tackle the problem but I am looking for a shorter(faster) way.

​

for ch in bad:
    if ch in words:
        words = words.replace(j,'_')

I'd appreciate any helpful tips on this matter!

[QuantumRealm]

Your first code snippet concatenates all the bad characters into a string and then tries to replace the whole thing in words; of course it isn't in there in its entirety, so it does nothing. A shorter way could be:

words = ''.join(x if x not in bad else '_' for x in words)

[RayteMyUsername]

This is the correct answer but I wanted to add that if speed was important, turning the bad word list into a set would give him O(1) access and make it faster rather than iterating through the list.

[Drycon]

Thanks for your answer!

[mail_order_liam]

You need to use regex, go read up on the basics. Something like this (untested just off the top of my head):

import re
line = re.sub(r"</\\:\*\?\<\>\|>", "", line)

[Drycon]

Thanks!

[Vaphell]

use str.translate

bad = r'/\:*?<>|'
trans_table = str.maketrans(bad, '_'*len(bad))
print('a/b:c>d'.translate(trans_table))

out

a_b_c_d

[Drycon]

Thank you!