Fix KeyError: '\s' when trying to replace a substring with one that includes special characters with re.sub() or re.subn() method

Question

import re

input_text = "Hello!, How are you? "

#input_text = re.sub(" ", r"[s|-|]", input_text)
input_text, nro_repl = re.subn(' ', r'[s|-|]', input_text)

print(repr(input_text))
print(repr(nro_repl))

The correct output:

4
'Hello!,[s|-|]How[s|-|]are[s|-|]you?[s|-|]'

The error that I get:

Traceback (most recent call last):
    this = chr(ESCAPES[this][1])
KeyError: '\s'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
    raise s.error('bad escape %s' % this, len(this))
re.error: bad escape s at position 1

How do I fix this error and get the desired result, managing to have the input string but making the replacements by substrings with the special characters?

Asked By: Matias Nicolas Rodriguez

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Source

Answer 1

In the manual that @Nick posted it tells us that there will be no backslash escape processing of the replacement if we pass a function instead of a string. So all you have to do is replace the string argument with a lambda returning the string.

import re

input_text = "Hello!, How are you? "
input_text, nro_repl = re.subn(' ', lambda x: '[s|-|]', input_text)

print(repr(nro_repl))
print(repr(input_text))

output:

4
'Hello!,[\s|-|]How[\s|-|]are[\s|-|]you?[\s|-|]'

Answered By: Onno Rouast

Fix KeyError: '\s' when trying to replace a substring with one that includes special characters with re.sub() or re.subn() method

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