def format_title_unicode_translate(title):
    return title.translate(title_unicode_trans)


class TitleUnicodeTranslate(dict):

    def __missing__(self, item):
        uni = chr(item)
res = '_'
if uni.isupper() or uni.islower():
    res = uni
self[item] = res
return res
title_unicode_trans = TitleUnicodeTranslate()
print(format_title_unicode_translate(
    'Metallica \u039c\u03b5\u03c4\u03b1\u03bb\u03bb\u03b9\u03ba\u03b1'))
Python - efficient method to remove all non-letters and replace them with underscores