## Challenge

Using Python, we want to convert words to numbers. In this challenge, we will explore how to convert a string into an integer.

The strings simply represent the numbers in words.

### 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

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

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