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Bill the Lizard
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>>> pattern = """... ^ # beginning of string... M{0,4} # thousands - 0 to 4 M's... (CM|CD|D?C{0,3}) # hundreds - 900 (CM), 400 (CD), 0-300 (0 to 3 C's),... # or 500-800 (D, followed by 0 to 3 C's)... (XC|XL|L?X{0,3}) # tens - 90 (XC), 40 (XL), 0-30 (0 to 3 X's),... # or 50-80 (L, followed by 0 to 3 X's)... (IX|IV|V?I{0,3}) # ones - 9 (IX), 4 (IV), 0-3 (0 to 3 I's),... # or 5-8 (V, followed by 0 to 3 I's)... $ # end of string... """>>> re.search(pattern, 'M', re.VERBOSE)>>> p = re.compile(r'(?P<word>\b\w+\b)')>>> m = p.search( '(((( Lots of punctuation )))' )>>> m.group('word')'Lots' You can also verbosely write a regex without usingre.VERBOSE thanks to string literal concatenation.
>>> pattern = (... "^" # beginning of string... "M{0,4}" # thousands - 0 to 4 M's... "(CM|CD|D?C{0,3})" # hundreds - 900 (CM), 400 (CD), 0-300 (0 to 3 C's),... # or 500-800 (D, followed by 0 to 3 C's)... "(XC|XL|L?X{0,3})" # tens - 90 (XC), 40 (XL), 0-30 (0 to 3 X's),... # or 50-80 (L, followed by 0 to 3 X's)... "(IX|IV|V?I{0,3})" # ones - 9 (IX), 4 (IV), 0-3 (0 to 3 I's),... # or 5-8 (V, followed by 0 to 3 I's)... "$" # end of string... )>>> print pattern"^M{0,4}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$">>> pattern = """ ^ # beginning of string M{0,4} # thousands - 0 to 4 M's (CM|CD|D?C{0,3}) # hundreds - 900 (CM), 400 (CD), 0-300 (0 to 3 C's), # or 500-800 (D, followed by 0 to 3 C's) (XC|XL|L?X{0,3}) # tens - 90 (XC), 40 (XL), 0-30 (0 to 3 X's), # or 50-80 (L, followed by 0 to 3 X's) (IX|IV|V?I{0,3}) # ones - 9 (IX), 4 (IV), 0-3 (0 to 3 I's), # or 5-8 (V, followed by 0 to 3 I's) $ # end of string """>>> re.search(pattern, 'M', re.VERBOSE)>>> p = re.compile(r'(?P<word>\b\w+\b)')>>> m = p.search( '(((( Lots of punctuation )))' )>>> m.group('word')'Lots'>>> pattern = """... ^ # beginning of string... M{0,4} # thousands - 0 to 4 M's... (CM|CD|D?C{0,3}) # hundreds - 900 (CM), 400 (CD), 0-300 (0 to 3 C's),... # or 500-800 (D, followed by 0 to 3 C's)... (XC|XL|L?X{0,3}) # tens - 90 (XC), 40 (XL), 0-30 (0 to 3 X's),... # or 50-80 (L, followed by 0 to 3 X's)... (IX|IV|V?I{0,3}) # ones - 9 (IX), 4 (IV), 0-3 (0 to 3 I's),... # or 5-8 (V, followed by 0 to 3 I's)... $ # end of string... """>>> re.search(pattern, 'M', re.VERBOSE)>>> p = re.compile(r'(?P<word>\b\w+\b)')>>> m = p.search( '(((( Lots of punctuation )))' )>>> m.group('word')'Lots' You can also verbosely write a regex without usingre.VERBOSE thanks to string literal concatenation.
>>> pattern = (... "^" # beginning of string... "M{0,4}" # thousands - 0 to 4 M's... "(CM|CD|D?C{0,3})" # hundreds - 900 (CM), 400 (CD), 0-300 (0 to 3 C's),... # or 500-800 (D, followed by 0 to 3 C's)... "(XC|XL|L?X{0,3})" # tens - 90 (XC), 40 (XL), 0-30 (0 to 3 X's),... # or 50-80 (L, followed by 0 to 3 X's)... "(IX|IV|V?I{0,3})" # ones - 9 (IX), 4 (IV), 0-3 (0 to 3 I's),... # or 5-8 (V, followed by 0 to 3 I's)... "$" # end of string... )>>> print pattern"^M{0,4}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$"
Readable regular expressions
In Python you can split a regular expression over multiple lines, name your matches and insert comments.
Example verbose syntax (fromDive into Python):
>>> pattern = """ ^ # beginning of string M{0,4} # thousands - 0 to 4 M's (CM|CD|D?C{0,3}) # hundreds - 900 (CM), 400 (CD), 0-300 (0 to 3 C's), # or 500-800 (D, followed by 0 to 3 C's) (XC|XL|L?X{0,3}) # tens - 90 (XC), 40 (XL), 0-30 (0 to 3 X's), # or 50-80 (L, followed by 0 to 3 X's) (IX|IV|V?I{0,3}) # ones - 9 (IX), 4 (IV), 0-3 (0 to 3 I's), # or 5-8 (V, followed by 0 to 3 I's) $ # end of string """>>> re.search(pattern, 'M', re.VERBOSE)Example naming matches (fromRegular Expression HOWTO)
>>> p = re.compile(r'(?P<word>\b\w+\b)')>>> m = p.search( '(((( Lots of punctuation )))' )>>> m.group('word')'Lots'lang-py