Python Pretty Print Numbers

prettyPrintNumber.py

from math import floor, log10
tinyNumbers = {
    1: "one",
    2: "two",
    3: "three",
    4: "four",
    5: "five",
    6: "six",
    7: "seven",
    8: "eight",
    9: "nine"
}
teens = {
    11: "eleven",
    12: "twelve",
    13: "thirteen",
    14: "fourteen",
    15: "fifteen",
    16: "sixteen",
    17: "seventeen",
    18: "eighteen",
    19: "nineteen",
}
multiplesOf10 = {
    10: "ten",
    20: "twenty",
    30: "thirty",
    40: "forty",
    50: "fifty",
    60: "sixty",
    70: "seventy",
    80: "eighty",
    90: "ninety",
}
powersOf10 = {
    10**2: "hundred",
    10**3: "thousand",
    10**6: "million",
    10**9: "billion",
    10**12: "trillion"
}
def prettyPrintNumber(num):
    assert num > 0, "Humans don't like {}".format(num)
    if num < 10:
        return tinyNumbers[num]
    elif num < 20 and num > 10:
        # Stupid humans insisting on special cases -_-
        return teens[num]
    elif num < 100:
        mult, remainder = divmod(num, 10)
        multStr = multiplesOf10[10*mult]
        parts = [multStr]
        if remainder > 0:
            parts.append(tinyNumbers[remainder])
        return ' '.join(parts)
    else:
        power = floor(log10(num))
        powerValue = 10**power
        while powerValue not in powersOf10:
            assert power > 2
            power -= 1
            powerValue = 10**power
        powerName = powersOf10[powerValue]
        powerMultiple, remainder = divmod(num, powerValue)
        assert powerMultiple < 1000, "Too large: {}".format(num)
        parts = [
            prettyPrintNumber(powerMultiple),
            powerName
        ]
        if remainder > 0:
            if remainder < 100:
                parts.append("and")
            parts.append(prettyPrintNumber(remainder))
        return ' '.join(parts)

def commaSeperated(num):
    digits = str(num)
    results = []
    remainder = len(digits) % 3
    if remainder:
        results.append(digits[:remainder])
    for index in range(remainder, len(digits), 3):
        results.append(digits[index:index + 3])
    return ','.join(results)

for testValue in (100, 342, 76, 1000000, 1307, 1046, 13, 13000):
    print("Pretty {}: {}".format(
        commaSeperated(testValue),
        prettyPrintNumber(testValue)
    ))