breaking loop in python

divyashree · 11-16-2014, 02:18 AM

I am writing a code to convert integer to roman.There are a lot of solution available in internet. But I am writing in this way in python:

Code:

#!/usr/bin/python
import sys

def convertToRoman( iinteger ):

        values = [ 1000, 900, 500, 400, 100, 90, 50, 40, 10, 5, 4,  1 ]
        symbolValues = { 1000 : 'M', 900 : 'CM', 500 : 'D', 400 : 'CD', 90 : 'XC', 100 : 'C', 50 : 'L', 40 : 'XL', 10 : 'X', 9 : 'IX', 5 : 'V', 4 : 'IV', 1 : 'I' }
        romanNumberList = []
        for value in values:
                rvalue = int(value)
                integer = int(iinteger)
                print integer,":",rvalue
                while  integer >= rvalue :
                        print integer,":",rvalue
                        romanNumberList.append(symbolValues[rvalue])
                        print romanNumberList
                        integer = integer - rvalue
                        print integer

                print "while finshing :", integer
        romanValue = ''.join(romanNumberList)
        print iinteger, ":", romanValue




number = sys.argv[1]
num = int(number)
if ( num > 2999):
        print "Bigger than expected 2999....exiting";
        sys.exit(2);
else:
        convertToRoman(num)

here I am not able to break the for loop .

example:

if input is 6: 6 compare to 5, gettng V, then 6-5=1 and 1 compared to 1 and getting I.
Now I got the roman as VI. and the loop should exit there.

instead of this, it again comparing 6 with 4, 6 with 1 from the values list.

Can anyone help me in this ??

norobro · 11-16-2014, 01:09 PM

Reverse your loops:

Code:

while input > 0
    loop over values
        if value <= input
            append roman numeral
            subtract value from input
            break

pan64 · 11-16-2014, 01:52 PM

the problem is the location of this line:
integer = int(iinteger)
this will reinitialize integer inside the for loop (and before the while cycle). This line should be put before the for cycle.

furthermore you missed the value 9 from the list of values, you ought to use:
for value in sorted(symbolValues.keys(),reverse=True):

dugan · 11-17-2014, 04:32 PM

try... except is a commonly accepted hack to break out of nested loops.

That said, if you really find yourself needed to break out of two loops then your code should be rewritten.