| 1 | n/a | """Convert to and from Roman numerals""" |
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| 2 | n/a | |
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| 3 | n/a | __author__ = "Mark Pilgrim (f8dy@diveintopython.org)" |
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| 4 | n/a | __version__ = "1.4" |
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| 5 | n/a | __date__ = "8 August 2001" |
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| 6 | n/a | __copyright__ = """Copyright (c) 2001 Mark Pilgrim |
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| 7 | n/a | |
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| 8 | n/a | This program is part of "Dive Into Python", a free Python tutorial for |
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| 9 | n/a | experienced programmers. Visit http://diveintopython.org/ for the |
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| 10 | n/a | latest version. |
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| 11 | n/a | |
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| 12 | n/a | This program is free software; you can redistribute it and/or modify |
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| 13 | n/a | it under the terms of the Python 2.1.1 license, available at |
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| 14 | n/a | http://www.python.org/2.1.1/license.html |
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| 15 | n/a | """ |
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| 16 | n/a | |
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| 17 | n/a | import re |
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| 18 | n/a | |
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| 19 | n/a | #Define exceptions |
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| 20 | n/a | class RomanError(Exception): pass |
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| 21 | n/a | class OutOfRangeError(RomanError): pass |
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| 22 | n/a | class NotIntegerError(RomanError): pass |
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| 23 | n/a | class InvalidRomanNumeralError(RomanError): pass |
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| 24 | n/a | |
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| 25 | n/a | #Define digit mapping |
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| 26 | n/a | romanNumeralMap = (('M', 1000), |
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| 27 | n/a | ('CM', 900), |
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| 28 | n/a | ('D', 500), |
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| 29 | n/a | ('CD', 400), |
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| 30 | n/a | ('C', 100), |
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| 31 | n/a | ('XC', 90), |
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| 32 | n/a | ('L', 50), |
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| 33 | n/a | ('XL', 40), |
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| 34 | n/a | ('X', 10), |
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| 35 | n/a | ('IX', 9), |
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| 36 | n/a | ('V', 5), |
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| 37 | n/a | ('IV', 4), |
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| 38 | n/a | ('I', 1)) |
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| 39 | n/a | |
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| 40 | n/a | def toRoman(n): |
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| 41 | n/a | """convert integer to Roman numeral""" |
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| 42 | n/a | if not (0 < n < 5000): |
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| 43 | n/a | raise OutOfRangeError("number out of range (must be 1..4999)") |
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| 44 | n/a | if int(n) != n: |
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| 45 | n/a | raise NotIntegerError("decimals can not be converted") |
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| 46 | n/a | |
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| 47 | n/a | result = "" |
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| 48 | n/a | for numeral, integer in romanNumeralMap: |
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| 49 | n/a | while n >= integer: |
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| 50 | n/a | result += numeral |
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| 51 | n/a | n -= integer |
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| 52 | n/a | return result |
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| 53 | n/a | |
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| 54 | n/a | #Define pattern to detect valid Roman numerals |
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| 55 | n/a | romanNumeralPattern = re.compile(""" |
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| 56 | n/a | ^ # beginning of string |
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| 57 | n/a | M{0,4} # thousands - 0 to 4 M's |
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| 58 | n/a | (CM|CD|D?C{0,3}) # hundreds - 900 (CM), 400 (CD), 0-300 (0 to 3 C's), |
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| 59 | n/a | # or 500-800 (D, followed by 0 to 3 C's) |
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| 60 | n/a | (XC|XL|L?X{0,3}) # tens - 90 (XC), 40 (XL), 0-30 (0 to 3 X's), |
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| 61 | n/a | # or 50-80 (L, followed by 0 to 3 X's) |
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| 62 | n/a | (IX|IV|V?I{0,3}) # ones - 9 (IX), 4 (IV), 0-3 (0 to 3 I's), |
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| 63 | n/a | # or 5-8 (V, followed by 0 to 3 I's) |
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| 64 | n/a | $ # end of string |
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| 65 | n/a | """ ,re.VERBOSE) |
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| 66 | n/a | |
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| 67 | n/a | def fromRoman(s): |
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| 68 | n/a | """convert Roman numeral to integer""" |
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| 69 | n/a | if not s: |
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| 70 | n/a | raise InvalidRomanNumeralError('Input can not be blank') |
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| 71 | n/a | if not romanNumeralPattern.search(s): |
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| 72 | n/a | raise InvalidRomanNumeralError('Invalid Roman numeral: %s' % s) |
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| 73 | n/a | |
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| 74 | n/a | result = 0 |
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| 75 | n/a | index = 0 |
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| 76 | n/a | for numeral, integer in romanNumeralMap: |
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| 77 | n/a | while s[index:index+len(numeral)] == numeral: |
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| 78 | n/a | result += integer |
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| 79 | n/a | index += len(numeral) |
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| 80 | n/a | return result |
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