mirror of
https://github.com/python/cpython.git
synced 2024-11-30 18:51:15 +01:00
81 lines
2.6 KiB
Python
81 lines
2.6 KiB
Python
"""Convert to and from Roman numerals"""
|
|
|
|
__author__ = "Mark Pilgrim (f8dy@diveintopython.org)"
|
|
__version__ = "1.4"
|
|
__date__ = "8 August 2001"
|
|
__copyright__ = """Copyright (c) 2001 Mark Pilgrim
|
|
|
|
This program is part of "Dive Into Python", a free Python tutorial for
|
|
experienced programmers. Visit http://diveintopython.org/ for the
|
|
latest version.
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
it under the terms of the Python 2.1.1 license, available at
|
|
http://www.python.org/2.1.1/license.html
|
|
"""
|
|
|
|
import re
|
|
|
|
#Define exceptions
|
|
class RomanError(Exception): pass
|
|
class OutOfRangeError(RomanError): pass
|
|
class NotIntegerError(RomanError): pass
|
|
class InvalidRomanNumeralError(RomanError): pass
|
|
|
|
#Define digit mapping
|
|
romanNumeralMap = (('M', 1000),
|
|
('CM', 900),
|
|
('D', 500),
|
|
('CD', 400),
|
|
('C', 100),
|
|
('XC', 90),
|
|
('L', 50),
|
|
('XL', 40),
|
|
('X', 10),
|
|
('IX', 9),
|
|
('V', 5),
|
|
('IV', 4),
|
|
('I', 1))
|
|
|
|
def toRoman(n):
|
|
"""convert integer to Roman numeral"""
|
|
if not (0 < n < 5000):
|
|
raise OutOfRangeError("number out of range (must be 1..4999)")
|
|
if int(n) != n:
|
|
raise NotIntegerError("decimals can not be converted")
|
|
|
|
result = ""
|
|
for numeral, integer in romanNumeralMap:
|
|
while n >= integer:
|
|
result += numeral
|
|
n -= integer
|
|
return result
|
|
|
|
#Define pattern to detect valid Roman numerals
|
|
romanNumeralPattern = re.compile("""
|
|
^ # 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.VERBOSE)
|
|
|
|
def fromRoman(s):
|
|
"""convert Roman numeral to integer"""
|
|
if not s:
|
|
raise InvalidRomanNumeralError('Input can not be blank')
|
|
if not romanNumeralPattern.search(s):
|
|
raise InvalidRomanNumeralError('Invalid Roman numeral: %s' % s)
|
|
|
|
result = 0
|
|
index = 0
|
|
for numeral, integer in romanNumeralMap:
|
|
while s[index:index+len(numeral)] == numeral:
|
|
result += integer
|
|
index += len(numeral)
|
|
return result
|