Challenge
Using Python, we want to convert words into numbers. In this challenge, we will explore how to convert a string into an integer.
The strings simply represent the numbers in words. Let’s convert these words into numbers.
Examples:
- “one” => 1
- “twenty” => 20
- “two hundred forty-six” => 246
- “seven hundred eighty-three thousand nine hundred and nineteen” => 783919
Additional Notes:
- The minimum number is “zero” (inclusively)
- The maximum number, which must be supported is 1 million (inclusively)
- The “and” in e.g. “one hundred and twenty-four” is optional, in some cases it’s present and in others, it’s not
- All tested numbers are valid, you don’t need to validate them
Test cases to convert words into numbers
Test.assert_equals(parse_int('one'), 1)
Test.assert_equals(parse_int('twenty'), 20)
Test.assert_equals(parse_int('two hundred forty-six'), 246)
The solution in Python to convert words into numbers
def parse_int(textnum, numwords={}):
# create our default word-lists
if not numwords:
# singles
units = [
"zero", "one", "two", "three", "four", "five", "six", "seven", "eight",
"nine", "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen",
"sixteen", "seventeen", "eighteen", "nineteen",
]
# tens
tens = ["", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"]
# larger scales
scales = ["hundred", "thousand", "million", "billion", "trillion"]
# divisors
numwords["and"] = (1, 0)
# perform our loops and start the swap
for idx, word in enumerate(units): numwords[word] = (1, idx)
for idx, word in enumerate(tens): numwords[word] = (1, idx * 10)
for idx, word in enumerate(scales): numwords[word] = (10 ** (idx * 3 or 2), 0)
# primary loop
current = result = 0
# loop while splitting to break into individual words
for word in textnum.replace("-"," ").split():
# if problem then fail-safe
if word not in numwords:
raise Exception("Illegal word: " + word)
# use the index by the multiplier
scale, increment = numwords[word]
current = current * scale + increment
# if larger than 100 then push for a round 2
if scale > 100:
result += current
current = 0
# return the result plus the current
return result + current
