CODEWITHSUNDEEP
python-3.xkeyerrorroman-numerals
JnooriRS
JnooriRS

Reputation: 93

How to overcome a keyError in roman numeral converter?

I feel confident that the logic of the code is correct, however, I come across keyError: 0.

def romanToInt(s: str) -> int:
    roman_table = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}
    result = 0

    for numeral in range(len(s)):
        if (
            numeral + 1 < len(s)
            and roman_table[s[numeral]] < roman_table[s[numeral + 1]]
        ):
            result -= roman_table[numeral]
        else:
            result += roman_table[numeral]

    return result


romanToInt("MCMXCIV")```

Below is the error in the terminal 

```$ python to_roman_numeral_converter.py
Traceback (most recent call last):
  File "C:Users\XYZ\dev\repos\roman_numeral\to_roman_numeral_converter.py", line 14, in <module>
    romanToInt("MCMXCIV")
  File "C:\Users\XYZ\dev\repos\roman_numeral\to_roman_numeral_converter.py", line 6, in romanToInt
    if numeral + 1 < len(s) and roman_table[numeral] < roman_table[numeral + 1]:
KeyError: 0

Not sure why it is not recognising roman_table value [numeral]?

Any help here is appreciated.

Upvotes: 1

Views: 60

Answers (1)

JnooriRS
JnooriRS

Reputation: 93

I manged to find out the problem

def romanToInt(s: str) -> int:
    roman_table = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}
    result = 0

    for numeral in range(len(s)):
        if (
            numeral + 1 < len(s)
            and roman_table[s[numeral]] < roman_table[s[numeral + 1]]
        ):
            result -= roman_table[s[numeral]]
        else:
            result += roman_table[s[numeral]]

    return result


romanToInt("MCMXCIV")

I was not accessing the value S

Upvotes: 1

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