Regex in Depth

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

Transcript

1. Regex In Depth
   

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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
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4. Abdur-Rahmaan Janhangeer
   Python
   Help people get into OpenSource
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5. Regex In Depth
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6. History of regex
   (from notes)
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7. import re
   
   pattern = re.compile(r'eee')
   result = pattern.match('eeee')
   
   print(result.group())
   
   eee
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8. import re
   
   pattern = re.compile(r'ike')
   result = pattern.search('like sike')
   
   print(result.group())
   
   ike
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9. import re
   
   pattern = re.compile(r'ike')
   result = pattern.findall('like sike')
   
   print(result)
   
   ['ike', 'ike']
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10. import re
    
    pattern = r'ike'
    
    string = 'like sike'
    
    result = re.findall(pattern, string)
    
    print(result)
    
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11. pattern = re.compile(
    
    r"...",
    
    re.MULTILINE)
    
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12. Patterns
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13. pattern = r"letter"
    
    string = "i wrote some letters from letters"
    
    ['letter', 'letter']
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14. pattern = r"l.tt.r"
    
    string = '''i wrote some letters
    
    from letters from the latter'''
    
    ['letter', 'letter', 'latter']
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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']
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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'
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17. pattern = r"\d{3}\D\d{3}\D\d{4}"
    
    string = '''Personal: +230 576-4321,
    
    Office: +230 671 2345''
    
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18. \w, \W
    pattern = r"\w"
    
    string = '''abc123_!^%£&£%$'''
    
    ['a', 'b', 'c', '1', '2', '3', '_']
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19. ^ start, $ end
    pattern = r"^\d$"
    
    string = '''234234234234234234'''
    
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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]
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21. [^exclude]
    pattern = r"l[^aeiou]ce"
    
    string = '''lice lace leece lyce lvce'''
    
    ['lyce', 'lvce']
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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']
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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']
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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']
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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']
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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')]
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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']
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28. Or
    pattern = re.compile(
    
    r"(?:Mr|Mrs){1}\.\s\w*")
    
    string = '''
    
    Mrs. sam Dr. sam Mr. Sam Miss. Sam
    
    '''
    
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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())
    
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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
    
    ?30
    

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31. Misc
    \b
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