Remove underscore from a list: Python

Question

Let's say I have the following list:

my_list = ['aaa', 'bb_bb', 'cc', 2]

I would like to remove underscore _ from a list element and would like to get

my_list = ['aaa', 'bbbb', 'cc', 2]

I tried this

my_list= [re.sub('_', '', _) for _ in my_list ]

For some reason I am getting an error TypeError: expected string or bytes-like object.

Can anyone help with this?

The last element of the list is an int and re.sub() knows nothing about it. — norok2
– norok2, Commented Aug 12, 2022 at 10:40

ljmc · Accepted Answer · 2022-08-12 10:46:35Z

7

It's because one of the elements is neither string nor bytes.

Also, you do not need re.sub to replace all instances of a character in a string, use str.replace instead, plus using _ as a variable name usually means it is ignored.

Try this instead:

[v.replace('_', '') if isinstance(v, str) else v for v in my_list]

edited Aug 12, 2022 at 10:46

answered Aug 12, 2022 at 10:40

ljmc

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Cow · Accepted Answer · 2022-08-12 10:42:10Z

1

Or if you absolutely must/want to stick to regex:

import re
my_list = ['aaa', 'bb_bb', 'cc', 2]
my_list= [re.sub('_', '', value) if isinstance(value, str) else value for value in my_list]
print(my_list)

Result:

['aaa', 'bbbb', 'cc', 2]

answered Aug 12, 2022 at 10:42

Cow

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2 Comments

ljmc Over a year ago

Yes, but it's much slower (and more computationally expensive), timing the str.replace method gives 1.42 µs ± 132 ns while the re.sub method gives 5.64 µs ± 113 ns.

Cow Over a year ago

@ljmc Yes, I know. Maybe some day it's not underscore anymore, but something more complicated, then regex could be something to consider. I'm just leaving this answer as someone else might need it in the future. I upvoted your answer too as I think it's better for this. :)

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