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I'm trying to use a regex to clean some data before I insert the items into the database. I haven't been able to solve the issue of removing trailing special characters at the end of my strings.

How do I write this regex to only remove trailing special characters?

import re strings = ['string01_','str_ing02_^','string03_@_', 'string04_1', 'string05_a_'] for item in strings: clean_this = (re.sub(r'([_+!@#$?^])', '', item)) print (clean_this) outputs this: string01 # correct string02 # incorrect because it remove _ in the string string03 # correct string041 # incorrect because it remove _ in the string string05a # incorrect because it remove _ in the string and not just the trailing _
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    Try [_+!@#$?^]+$ Commented Dec 18, 2018 at 16:19

3 Answers 3

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6

You could also use the special purpose rstrip method of strings

[s.rstrip('_+!@#$?^') for s in strings] # ['string01', 'str_ing02', 'string03', 'string04_1', 'string05_a']
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Thanks for pointing out this method, because I haven't seen it before.
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You could repeat the character class 1+ times or else only 1 special character would be replaced. Then assert the end of the string $. Note that you don't need the capturing group around the character class:

[_+!@#$?^]+$

For example:

import re strings = ['string01_','str_ing02_^','string03_@_', 'string04_1', 'string05_a_'] for item in strings: clean_this = (re.sub(r'[_+!@#$?^]+$', '', item)) print (clean_this)

See the Regex demo | Python demo

If you also want to remove whitespace characters at the end you could add \s to the character class:

[_+!@#$?^\s]+$

Regex demo

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4 Comments

For some reason, certain strings aren't being removed, such as 05_+_
my current regex is this: (re.sub(r'[!@#$%^&*<>?_\s]+$', '', item))
It seems to work ideone.com/qfhM1I Can you share the code where you pull the values from the list?
It seems that the key was changing str(item_name).strip().lower() to repr(item_name).strip().lower() in the section of code that created the list containing the data.
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You need an end-of-word anchor $

 clean_this = (re.sub(r'[_+!@#$?^]+$', '', item))

Demo

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5 Comments

This works, but for some odd reason in my production data items that end with _ are not always removed.
Could you show examples of data that cause those issues?
some of the production data strings not being cleaned at the end: on_+_ , 05____ , 50__j_
Are you sure there is no trailing whitespace?
It seems that the key was changing str(item_name).strip().lower() to repr(item_name).strip().lower() in the section of code that created the list containing the data.

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