Python base 36 encoding

Have you tried Wikipedia's sample code?

def base36encode(number, alphabet='0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'):
    """Converts an integer to a base36 string."""
    if not isinstance(number, (int, long)):
        raise TypeError('number must be an integer')

    base36 = ''
    sign = ''

    if number < 0:
        sign = '-'
        number = -number

    if 0 <= number < len(alphabet):
        return sign + alphabet[number]

    while number != 0:
        number, i = divmod(number, len(alphabet))
        base36 = alphabet[i] + base36

    return sign + base36

def base36decode(number):
    return int(number, 36)

print base36encode(1412823931503067241)
print base36decode('AQF8AA0006EH')

I wish I had read this before. Here is the answer:

def base36encode(number):
    if not isinstance(number, (int, long)):
        raise TypeError('number must be an integer')
    is_negative = number < 0
    number = abs(number)

    alphabet, base36 = ['0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ', '']

    while number:
        number, i = divmod(number, 36)
        base36 = alphabet[i] + base36
    if is_negative:
        base36 = '-' + base36

    return base36 or alphabet[0]


def base36decode(number):
    return int(number, 36)

print(base36encode(1412823931503067241))
print(base36decode('AQF8AA0006EH'))
assert(base36decode(base36encode(-9223372036721928027)) == -9223372036721928027)

I benchmarked the example encoders provided in answers to this question. On my Ubuntu 18.10 laptop, Python 3.7, Jupyter, the %%timeit magic command, and the integer 4242424242424242 as the input, I got these results:

• Wikipedia's sample code: 4.87 µs ± 300 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
• @mistero's base36encode(): 3.62 µs ± 44.2 ns per loop
• @user1036542's int2base: 10 µs ± 400 ns per loop (after fixing py37 compatibility)
• @mbarkhau's int_to_base36(): 3.83 µs ± 28.8 ns per loop

All timings were mean ± std. dev. of 7 runs, 100000 loops each.

If you are feeling functional

def b36_encode(i):
    if i < 0: return "-" + b36_encode(-i)
    if i < 36: return "0123456789abcdefghijklmnopqrstuvwxyz"[i]
    return b36_encode(i // 36) + b36_encode(i % 36)    

test

n = -919283471029384701938478
s = "-45p3wubacgd6s0fi"
assert int(s, base=36) == n
assert b36_encode(n) == s