Regex

Regex Case Insensitive Matching: The 'i' Flag Explained! - YouTube

September 5, 2025

07:33

Case Insensitive Matching in Python with .Casefold() - YouTube

January 30, 2023

13:44

Python Tips and Tricks: Case-Insensitive String Comparisons Done ...

July 11, 2022

youtube.com

Mastering Case-Insensitive Regex: Python, Java, and JavaScript

03:36

python regex match ignore case - YouTube

January 21, 2024

youtube.com

You’re doing case-insensitive sorts WRONG #python #coding ...

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AskPython

askpython.com › python-modules › python-regex-for-case-insensitive-text-matching

Python Regex for Case-Insensitive Text Matching without re.compile() - AskPython

May 12, 2023 - re.sub()-> This function replaces the matched string of the expression and replaces it with something else. Related: Matching Entire Strings in Python using Regular Expressions.

stackoverflow.com › questions › 500864 › case-insensitive-regular-expression-without-re-compile

python - Case insensitive regular expression without re.compile? - Stack Overflow

1 of 11

881

Pass re.IGNORECASE to the flags param of search, match, or sub:

re.search('test', 'TeSt', re.IGNORECASE)
re.match('test', 'TeSt', re.IGNORECASE)
re.sub('test', 'xxxx', 'Testing', flags=re.IGNORECASE)

2 of 11

162

You can also perform case insensitive searches using search/match without the IGNORECASE flag (tested in Python 2.7.3):

re.search(r'(?i)test', 'TeSt').group()    ## returns 'TeSt'
re.match(r'(?i)test', 'TeSt').group()     ## returns 'TeSt'

stackoverflow.com › questions › 919056 › case-insensitive-replace

python - Case insensitive replace - Stack Overflow

w3resource.com › python-exercises › re › python-re-exercise-44.php

1 of 11

296

The string type doesn't support this. You're probably best off using the regular expression sub method with the re.IGNORECASE option.

>>> import re
>>> insensitive_hippo = re.compile(re.escape('hippo'), re.IGNORECASE)
>>> insensitive_hippo.sub('giraffe', 'I want a hIPpo for my birthday')
'I want a giraffe for my birthday'

2 of 11

117

import re
pattern = re.compile("hello", re.IGNORECASE)
pattern.sub("bye", "hello HeLLo HELLO")
# 'bye bye bye'

w3resource

Python: Do a case insensitive string replacement - w3resource

Write a Python program to do case-insensitive string replacement. ... import re text = "PHP Exercises" print("Original Text: ",text) redata = re.compile(re.escape('php'), re.IGNORECASE) new_text = redata.sub('php', 'PHP Exercises') print("Using 'php' replace PHP") print("New Text: ",new_text)

Mycoding

mycoding.uk › a › python__how_to_do_case_insensitive_string_replacement.html

Python: How to do Case insensitive string replacement

Also, we will pre-compile search patter into regular expression for future use with ignoring case · import re # import module for regular expressions test_string = 'One two oNe Two onE tWo ONE TWO one tWO' # string to be replaces pattern = 'two' # pattern for seach replace = '222' # patter for replacement #replace = 'TWO' compiled = re.compile(re.escape(pattern), re.IGNORECASE) # pre-compiled pattern new_string = compiled.sub(replace, test_string) # replace with pre-compiled pattern print( new_string) # One 222 oNe 222 onE 222 ONE 222 one 222

Find elsewhere

Google Bing Mojeek

stackoverflow.com › questions › 44831689 › issue-with-case-insensitive-regex-pattern-for-re-sub

python - Issue with case-insensitive regex pattern for re.sub() - Stack Overflow

realpython.com › lessons › replace-string-python-case-insensitive

1 of 1

Regex

The regular expression is \.1dc\.com. The backslash escapes the dot which normally matches any character rather than just a period.

Make the search case insensitive with the re.IGNORECASE flag.

Find and eliminate the target expression using re.sub().

Full solution

import re

data = [
    {'system_name': 'a1pvdb092', 'fdc_inv_sa_team': 'X2AIX_GBS'},
    {'system_name': 'W00000001.1DC.com', 'fdc_inv_sa_team': 'LAA.BRAZIL.AAA.WINDOWS\n'},
    {'system_name': 'a10000048', 'fdc_inv_sa_team': 'X2AIX_NSS'},
    {'system_name': 'a10000049', 'fdc_inv_sa_team': 'X2AIX_NSS'},
]

for row in data:
    sysname = row['system_name']
    print([re.sub(r'\.1dc\.com', '', sysname, flags=re.IGNORECASE)])

Output

['a1pvdb092']
['W00000001']
['a10000048']
['a10000049']

Real Python

Be Case-Insensitive (Video) – Real Python

02:08

Be Case-Insensitive 02:08 · Look for a Character Set 01:55 · Append a Quantifier 02:18 · Recap Your Regex Patterns 00:13 · Working With Regular Expressions · Get to Know re.sub() 01:09 · Use re.sub() 05:11 · Replace a String in Python (Summary) 02:08 ·

Published: August 22, 2023

LearnByExample

learnbyexample.github.io › py_regular_expressions › flags.html

Flags - Understanding Python re(gex)?

1) Remove from the first occurrence of hat to the last occurrence of it for the given input strings. Match these markers case insensitively. >>> s1 = 'But Cool THAT\nsee What okay\nwow quite' >>> s2 = 'it this hat is sliced HIT.' >>> pat = re.compile() ##### add your solution here >>> pat.sub('', s1) 'But Cool Te' >>> pat.sub('', s2) 'it this .'

ProgramCreek

programcreek.com › python › example › 96 › re.IGNORECASE

Python Examples of re.IGNORECASE

def normalize_release_tags(name, real_title): import re import xbmc def _normalize_name(val): proper = re.sub(r"[\[$\]$]", "", val) proper = re.sub(r"'", "", proper) proper = re.sub(r"\W", " ", proper) proper = re.sub(r"\s+", " ", proper) return proper name = _normalize_name(name) real_title = _normalize_name(real_title) release_tags = re.compile(real_title, re.IGNORECASE).sub("", name) tags = map(re.escape, VIDEO_CODECS.keys() + AUDIO_CODECS.keys() + RESOLUTIONS.keys()) release_tags = re.compile("(%s)" % "|".join(tags), re.IGNORECASE).sub("", release_tags) release_tags = re.sub(r"\s+", " ", release_tags) return release_tags.strip()

Real Python

realpython.com › lessons › replace-string-python-resub

Use re.sub() (Video) – Real Python

05:11

The re.IGNORECASE flag makes it a case-insensitive pattern. So now any substring containing "blast", regardless of capitalization, will be matched and replaced. And finally, you print the transcript again.

Published: August 22, 2023

Finxter

blog.finxter.com › 5-best-ways-to-perform-case-insensitive-string-replacement-in-python

5 Best Ways to Perform Case Insensitive String Replacement in Python – Be on the Right Side of Change

February 27, 2024 - This code snippet first imports the re module. It then defines a pattern to look for in the text, a replacement string, and uses the re.sub() function, passing the re.IGNORECASE flag to replace all case insensitive occurrences of the pattern with the replacement string.

Index.dev

index.dev › blog › regex-advanced-string-replacement-python

Python Regex Replace: How to Replace Strings Using re Module

By default, regex in Python is case-sensitive. If you want to perform case-insensitive replacements, you can use the re.IGNORECASE flag. Additionally, regex can work across multiple lines if the string contains line breaks.

TutorialsPoint

tutorialspoint.com › article › case-insensitive-string-replacement-using-python-program

Case-insensitive string replacement using Python Program

March 26, 2026 - You can use the (?i) inline flag for case-insensitive matching without compiling ? import re input_string = "Hello TutorialsPOINT Python" substring = "tutorialspoint" replace_string = "Java" # use (?i) for case-insensitive matching result = re.sub('(?i)' + re.escape(substring), replace_string, input_string) print("Result:", result)

stackoverflow.com › questions › 8813265 › why-doesnt-ignorecase-flag-re-i-work-in-re-sub

python - Why doesn't ignorecase flag (re.I) work in re.sub() - Stack Overflow

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114

Seems to me that you should be doing:

import re
print(re.sub('class', 'function', 'Class object', flags=re.I))

Without this, the re.I argument is passed to the count argument.

2 of 5

The flags argument is the fifth one - you're passing the value of re.I as the count argument (an easy mistake to make).

stackoverflow.com › questions › 787842 › case-insensitivity-in-python-strings

Case insensitivity in Python strings - Stack Overflow

reddit.com › r/learnpython › regex re.sub() not working as expected

1 of 3

You can supply the flag re.IGNORECASE to functions in the re module as described in the docs.

matcher = re.compile(myExpression, re.IGNORECASE)

2 of 3

Using re is the best solution even if you think it's complicated.

To replace all occurrences of 'abc', 'ABC', 'Abc', etc., with 'Python', say:

re.sub(r'(?i)abc', 'Python', a)

Example session:

>>> a = 'abc  asd   Abc  asd  ABCDE    XXAbCXX'
>>> import re
>>> re.sub(r'(?i)abc', 'Python', a)
'Python  asd   Python  asd  PythonDE    XXPythonXX'
>>>

Note how embedding (?i) at the start of the regexp makes it case insensitive. Also note the r'...' string literal for the regexp (which in this specific case is redundant but helps as soon as you use a regexp that has backslashes (\) in them.

r/learnpython on Reddit: regex re.sub() not working as expected

October 11, 2022 -

What am I missing here? I am doing a re.sub() call with re.IGNORECASE, but it is clearly NOT ignoring the case :/

import re
for txt in ["This is line 1.", "This is LINE 2."]:
    print(re.sub(rf"(\W)(line)(\W)", r"\1<\2>\3", txt, re.I))

The output of the above is

This is <line> 1.
This is LINE 2.

As you can see, re.sub() appears to be case-sensitive, even though I have the flag re.I. I tried compiling the expression and got the same results.

Any feedback is greatly appreciated. Thank you