re.sub() doesn't substitute for all words with the replacement in the string when re.IGNORECASE is used and counter not specified

[abhii2003]

# Bug report

re.sub() doesn't substitute for all words with the replacement in the string when re.IGNORECASE is used.

# Your environment
This bug was experienced on IDLE and VS code

#Problem
Whenever re.sub() is used with the flag re.IGNORECASE or re.I and, the counter is not specified all of the occurrences of the word were not replaced instead only the first 2 occurrences were replaced.

For example if the replacement is a string "cat" which should replace the word dog,
The code :
import re
print(re.sub("dog","cat","dog and cat and dog and dog and dog",re.I))
or
import re
print(re.sub("dog","cat","dog and cat and dog and dog and dog",re.IGNORECASE))

the expected output was :
cat and cat and cat and cat and cat

the actual output is:
cat and cat and cat and dog and dog

below is the image of the editor depicting the problem

[abhii2003]

Can someone please help and guide me to contribute to solving the issue?

[hauntsaninja]

Duplicate of #85830

I recommend using keyword args: print(re.sub("dog","cat","dog and cat and dog and dog and dog", flags=re.I))

I'm leaving open in case anyone is interested in deprecating passing count by position — this is a little bit of a footgun

[hauntsaninja]

Okay, looks like this is a super common point of confusion, so we should do something. Time to go through the following issues and figure out what Serhiy's opinion on this: #89621, #86639, #85930, #85830, #79724, #75110, #73091, #72038, #70542, #66949, #61863, #59972, #56287, #56166, #56156, #55471

[hauntsaninja]

Okay, closing and will discuss on #56166

[abhii2003]

okay that is good