titlecasing: using pyicu, or to_title(), a wrapper to python's inbuilt method str.title().

icu_totitle.py

from icu import Locale, UnicodeString
# loc = Locale.createCanonical("haw_US")
loc = Locale("haw_US")
s1 = "ʻōlelo hawaiʻi"
s2 = "oude ijssel   "
print(UnicodeString(s1).toTitle(loc))
print(UnicodeString(s2).toTitle(Locale("nl_NL")).trim())

to_title.py

import regex as re
def to_title(s, hyphens=False):
    def slice_group(grp):
        if grp.group(0)[0] == "ʻ":
            return grp.group(0)[0] + grp.group(0)[1].upper() + grp.group(0)[2:].lower()
        else:
            return grp.group(0)[0].upper() + grp.group(0)[1:].lower()
    pattern = r"[ʻ]?[\p{Alphabetic}]+([\-'·:\uA789\u2019]?[\p{Alphabetic}\p{Mn}\p{Mc}])+" if hyphens else r"[ʻ]?[\p{Alphabetic}]+(['·:\uA789\u2019]?[\p{Alphabetic}\p{Mn}\p{Mc}])+" 
    regexPattern = re.compile(pattern, re.I)
    return regexPattern.sub(lambda grp: slice_group(grp), s)


s1 = "ʻōlelo hawaiʻi"
print(to_title(s1))