Re: Case insensitive replacement?

[MRAB]

On 2016-09-27 17:56, Tim Chase wrote:
I'd like to do a case-insensitive replacement in a string but want to
do it pythonically.  Ideally, the code would something like  needle = "World"
  haystack = "Hello, world!"
  replacement = "THERE"
  result = haystack.replace(needle, replacement, ignore_case=True)
  # result would be "Hello, THERE!"

As that's not an option, I can do it either with string-hacking:

  try:
    index = haystack.upper().find(needle.upper())
  except ValueError:
    result = haystack
  else:
    result = (
      haystack[:index]
      + replacement
      + haystack[index + len(needle):]
      )

The disadvantage of your "string-hacking" is that you're assuming that 
the uppercase version of a string is the same length as the original:
That's not always the case:

Python 3.5.1 (v3.5.1:37a07cee5969, Dec  6 2015, 01:54:25) [MSC v.1900 64 
bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> '\N{LATIN SMALL LETTER SHARP S}'
'ß'
>>> '\N{LATIN SMALL LETTER SHARP S}'.upper()
'SS'
>>>

or with regexes:

  import re
  r = re.compile(re.escape(needle), re.I)
  result = r.sub(replacement, haystack)

The regex version is certainly tidier, but it feels a bit like
killing a fly with a rocket-launcher.

Are there other/better options that I've missed?

Also, if it makes any difference, my replacement in this use-case is
actually deletion, so replacement=""

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