How can I encode an integer with base 36 in Python and then decode it again?
Chris
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asked Jul 25, 2009 at 11:32
1
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 >> import base36
>>> assert base36.dumps[19930503] == 'bv6h3'
>>> assert base36.loads['bv6h3'] == 19930503
answered Jul 15, 2016 at 5:21
Jiangge ZhangJiangge Zhang
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4
terrible answer, but was just playing around with this an thought i'd share.
import string, math
int2base = lambda a, b: ''.join[
[[string.digits +
string.ascii_lowercase +
string.ascii_uppercase][[a // b ** i] % b]
for i in range[int[math.log[a, b]], -1, -1]]
]
num = 1412823931503067241
test = int2base[num, 36]
test2 = int[test, 36]
print test2 == num
akaihola
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answered Jul 10, 2012 at 4:43
3
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.
answered Apr 27, 2019 at 16:53
akaiholaakaihola
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1
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
answered Mar 2, 2020 at 23:24
1
This works if you only care about positive integers.
def int_to_base36[num]:
"""Converts a positive integer into a base36 string."""
assert num >= 0
digits = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
res = ''
while not res or num > 0:
num, i = divmod[num, 36]
res = digits[i] + res
return res
To convert back to int, just use int[num, 36]. For a conversion of arbitrary bases see //gist.github.com/mbarkhau/1b918cb3b4a2bdaf841c
answered Jul 31, 2015 at 13:02
mbarkhaumbarkhau
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