port of BLI_strcasecmp_natural from C++ to Python, not tested very much

from functools import cmp_to_key
#from source/blender/blenlib/intern/string.c/BLI_strcasecmp_natural for Blender 4.1.1
def BLI_strcasecmp_natural(s1, s2):
  #there's no dedicated str.compare function in Python
  def strcmp(s1, s2):
    if s1 < s2:
      return -1
    elif s1 > s2:
      return 1
    else:
      return 0
  #compare number on the left size of the string
  def left_number_strcmp(s1, s2, tiebreaker2):
    p1 = 0
    p2 = 0
    numdigit = 0
    numzero1 = 0
    numzero2 = 0
    #count and skip leading zeros
    while s1[p1] == '0':
      p1 += 1
      numzero1 += 1
    while s2[p2] == '0':
      p2 += 1
      numzero2 += 1
    #find number of consecutive digits
    while True:
      if s1[p1+numdigit].isdigit() and s2[p2+numdigit].isdigit():
        numdigit += 1
        continue
      if s1[p1+numdigit].isdigit():
        return 1 #s2 is bigger
      if s2[p2+numdigit].isdigit():
        return -1 #s1 is bigger
      break
    #same number of digits, compare size of number
    if numdigit > 0:
      compare = strcmp(s1[p1:p1+numdigit], s2[p2:p1+numdigit])
      if compare != 0:
        return compare
    #use number of leading zeros as tie breaker if still equal
    if tiebreaker2[0] == 0:
      if numzero1 > numzero2:
        tiebreaker2[0] = 1
      elif numzero1 < numzero2:
        tiebreaker2[0] = -1
    return 0
  s1 += '\0'
  s2 += '\0'
  d1 = 0
  d2 = 0
  c1 = None
  c2 = None
  tiebreaker = 0
  #if both chars are numeric, to a left_number_strcmp().
  #then increase string deltas as long they are
  #numeric, else do a tolower and char compare
  while True:
    if s1[d1].isdigit() and s2[d2].isdigit():
      tiebreaker2 = [tiebreaker]
      numcompare = left_number_strcmp(s1[d1:], s2[d2:], tiebreaker2)
      tiebreaker = tiebreaker2[0]
      if numcompare != 0:
        return numcompare
      #Some wasted work here, left_number_strcmp already consumes at least some digits.
      d1 += 1
      while s1[d1].isdigit():
        d1 += 1
      d2 += 1
      while s2[d2].isdigit():
        d2 += 1
    #Test for end of strings first so that shorter strings are ordered in front.
    if '\0' in [s1[d1], s2[d2]]:
      break
    c1 = s1[d1].lower()
    c2 = s2[d2].lower()
    if c1 == c2:
      #Continue iteration
      pass
    #Check for '.' so "foo.bar" comes before "foo 1.bar".
    elif c1 == '.':
      return -1
    elif c2 == '.':
      return 1
    elif c1 < c2:
      return -1
    elif c1 > c2:
      return 1
    d1 += 1
    d2 += 1
  if tiebreaker != 0:
    return tiebreaker
  #we might still have a different string because of lower/upper case, in
  #that case fall back to regular string comparison
  return strcmp(s1, s2)
print(sorted(["a", "A", "c", "b", "d", "foo.bar", "foo 1.bar", "a.00", "a.001", "a.002", "a.000"], key=cmp_to_key(BLI_strcasecmp_natural)))