Regex in Depth

Explains the history of regex in depth as well as covering all features in a practise-oriented way!

1. Regex In Depth
3. Python Mauritius UserGroup (pymug) More info: mscc.mu/python-mauritius-usergroup-pymug/ Why Where codes github.com/pymug share events twitter.com/pymugdotcom ping professionals linkedin.com/company/pymug all info pymug.com tell friends by like facebook.com/pymug 3
4. Abdur-Rahmaan Janhangeer Python Help people get into OpenSource 4
5. Regex In Depth 5
6. History of regex (from notes) 6
7. import re pattern = re.compile(r'eee') result = pattern.match('eeee') print(result.group()) eee 7
8. import re pattern = re.compile(r'ike') result = pattern.search('like sike') print(result.group()) ike 8
9. import re pattern = re.compile(r'ike') result = pattern.findall('like sike') print(result) ['ike', 'ike'] 9
10. import re pattern = r'ike' string = 'like sike' result = re.findall(pattern, string) print(result) 10
11. pattern = re.compile( r"...", re.MULTILINE) 11
12. Patterns 12
13. pattern = r"letter" string = "i wrote some letters from letters" ['letter', 'letter'] 13
14. pattern = r"l.tt.r" string = '''i wrote some letters from letters from the latter''' ['letter', 'letter', 'latter'] 14
15. \d digit pattern = r"\d\d\d.\d\d\d\d\d\d\d" string = '''Personal: +230 5764321, Office: +230 6712345''' ['230 5764321', '230 6712345'] 15
16. \s - space \D - non digit try: r"\+\d\d\d\s\d\d\d\d\d\d\d" r".\d\d\d\s\d\d\d\d\d\d\d" r".\d\d\d\s\d\d\d\d\d\d\d" pattern = r"\d\d\d\D\d\d\d\D\d\d\d\d" string = '''Personal: +230 576-4321, Office: +230 671 2345''' r'\d' 16
17. pattern = r"\d{3}\D\d{3}\D\d{4}" string = '''Personal: +230 576-4321, Office: +230 671 2345'' 17
18. \w, \W pattern = r"\w" string = '''abc123_!^%£&£%$''' ['a', 'b', 'c', '1', '2', '3', '_'] 18
19. ^ start, $ end pattern = r"^\d$" string = '''234234234234234234''' 19
20. [abcd] range of chars pattern = r"l[aeiou]ce" string = '''lice lace leece lyce lvce''' ['lice', 'lace'] try: [a-z] [A-Z] [0-9] [a-zA-z] 20
21. [^exclude] pattern = r"l[^aeiou]ce" string = '''lice lace leece lyce lvce''' ['lyce', 'lvce'] 21
22. Repeat x{1, 3} pattern = r"lo{2,5} and behold" string = '''loo and behold lo and behold looooo and behold looo and behold loooooo and behold''' ['loo and behold', 'looooo and behold', 'looo and behold'] 22
23. 0 or more pattern = r"lo* and behold" string = ''' loo and behold lo and behold looooo and behold looo and behold loooooo and behold l and behold''' ['loo and behold', 'lo and behold', 'looooo and behold', 'looo and behold', 'loooooo and behold', 'l and behold'] 23
24. at least once pattern = r"lo+ and behold" string = ''' loo and behold lo and behold looooo and behold looo and behold loooooo and behold l and behold''' ['loo and behold', 'lo and behold', 'looooo and behold', 'looo and behold', 'loooooo and behold'] 24
25. 0 or 1 pattern = r"lo? and behold" string = ''' loo and behold lo and behold looooo and behold looo and behold loooooo and behold l and behold''' ['lo and behold', 'l and behold'] 25
26. Capturing pattern = re.compile( r"i bought (cat)?\s?(dog)?\s?(mouse)?") string = ''' i bought cat i bought dog i bought mouse i bought cat dog i bought cat mouse ''' [('cat', '', ''), ('', 'dog', ''), ('', '', 'mouse'), ('cat', 'dog', ''), ('cat', '', 'mouse')] 26
27. (?:) pattern = re.compile( r"i bought (?:cat)?\s?(?:dog)?\s?(?:mouse)?") string = ''' i bought cat i bought dog i bought mouse i bought cat dog i bought cat mouse ''' ['i bought cat \n', 'i bought dog\n', 'i bought mouse', 'i bought cat dog\n', 'i bought cat mouse'] 27
28. Or pattern = re.compile( r"(?:Mr|Mrs){1}\.\s\w*") string = ''' Mrs. sam Dr. sam Mr. Sam Miss. Sam ''' 28
29. Capturing and backref import re pattern = re.compile( r"(a)l\1") string = ''' ala alo ali ''' result = re.search(pattern, string) print(result.group()) 29
30. look ahead if there is not return match pattern = re.compile( r"c(?=[aeiou])+") string = ''' coo ca ci cw ''' ['c', 'c', 'c'] ?! not followed by ?<= look behind ?<! not behind 30
31. Misc \b 31