Transform case using RegExp

regex_transform_case.py

import unittest
import re

class RegexTransformCase(unittest.TestCase):
    def setUp(self):
        self.pattern = r'(?<!\\)\\(U|L)(.*?)(?<!\\)\\[ELU]'

        self.upper_strings = [
            (r'\Uhello\E', r'HELLO'),
            (r'\\Uhello\E', r'\\Uhello\E'),
            (r'\Uhello\\E', r'\Uhello\\E'),
            (r'\\Uhello\\E', r'\\Uhello\\E'),
        ]
        self.lower_strings = [
            (r'\LHELLO\E', r'hello'),
            (r'\\LHELLO\E', r'\\LHELLO\E'),
            (r'\LHELLO\\E', r'\LHELLO\\E'),
            (r'\\LHELLO\\E', r'\\LHELLO\\E'),
        ]

        for pattern, string in tuple(self.upper_strings):
            self.upper_strings.append(('test%s' % pattern, 'test%s' % string))
            self.upper_strings.append(('%stest' % pattern, '%stest' % string))
            self.upper_strings.append(('test%stest' % pattern, 'test%stest' % string))
        for pattern, string in tuple(self.lower_strings):
            self.lower_strings.append(('test%s' % pattern, 'test%s' % string))
            self.lower_strings.append(('%stest' % pattern, '%stest' % string))
            self.lower_strings.append(('test%stest' % pattern, 'test%stest' % string))

        for pattern, string in tuple(self.upper_strings):
            self.upper_strings.append((pattern.replace('test', r'te\\st'), string.replace('test', r'te\\st')))
            self.upper_strings.append((pattern.replace('test', r'te\\Et'), string.replace('test', r'te\\Et')))
            self.upper_strings.append((pattern.replace('test', r'te\\Lt'), string.replace('test', r'te\\Lt')))
            self.upper_strings.append((pattern.replace('test', r'te\\Ut'), string.replace('test', r'te\\Ut')))
        for pattern, string in tuple(self.lower_strings):
            self.lower_strings.append((pattern.replace('test', r'te\\st'), string.replace('test', r'te\\st')))
            self.lower_strings.append((pattern.replace('test', r'te\\Et'), string.replace('test', r'te\\Et')))
            self.lower_strings.append((pattern.replace('test', r'te\\Lt'), string.replace('test', r'te\\Lt')))
            self.lower_strings.append((pattern.replace('test', r'te\\Ut'), string.replace('test', r'te\\Ut')))

        for pair in tuple(self.upper_strings):
            print pair
        for pair in tuple(self.lower_strings):
            print pair

    def regex(self, string):
        def repl(match):
            if match.group(1) == 'U':
                return match.group(2).upper()
            elif match.group(1) == 'L':
                return match.group(2).lower()
        return re.sub(self.pattern, repl, string)

    def test_upper(self):
        for pattern, string in self.upper_strings:
            self.assertEqual(self.regex(pattern), string)
            print self.regex(pattern), string

    def test_lower(self):
        for pattern, string in self.lower_strings:
            self.assertEqual(self.regex(pattern), string)
            print self.regex(pattern), string

if __name__ == '__main__':
    unittest.main()