Uneven base-36 support in Python?

Question

I've been working with base-36 recently and have never been satisfied with the usual answer to converting ints into base-36 strings. It looks a little imbalanced…

def to_base36(value):
    if not isinstance(value, int):
        raise TypeError("expected int, got %s: %r" % (value.__class__.__name__, value))

    if value == 0:
        return "0"

    if value < 0:
        sign = "-"
        value = -value
    else:
        sign = ""

    result = []

    while value:
        value, mod = divmod(value, 36)
        result.append("0123456789abcdefghijklmnopqrstuvwxyz"[mod])

    return sign + "".join(reversed(result))

…when compared to converting back…

def from_base36(value):
    return int(value, 36)

Does Python really not include this particular battery?

score 8 · Answer 1 · answered Nov 23 '10 at 05:41

8

Have you tried the basin package?

>>> import basin
>>> basin.encode("0123456789abcdefghijklmnopqrstuvwxyz", 100)
'2s'

It's not batteries included, but the pypi repository is like a convenience store for picking up batteries with the minimum of fuss.

answered Nov 23 '10 at 05:41

fmark

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score 4 · Accepted Answer · answered Nov 23 '10 at 05:29

4

Correct. Not every store carries N or J batteries.

answered Nov 23 '10 at 05:29

Ignacio Vazquez-Abrams

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+1, base 36 is rather unusual, so including it in the standard library would just add bloat – Rafe Kettler Nov 23 '10 at 05:33
6

@Rafe — To me, it's less base36 specifically, but that Python includes support for converting *from* arbitrary bases but not *to* them. – Ben Blank Nov 23 '10 at 05:34
Rafe: Yet it's apparently not so unusual, nor the 'bloat' so bad, to warrant removing from `int()`! – Ken Nov 23 '10 at 05:36
@Ben yes, that would make sense. – Rafe Kettler Nov 23 '10 at 05:41
3

Standard C has the same asymmetry. – dan04 Nov 23 '10 at 05:48
4

... which is probably a big clue as to why Python also has the asymmetry - as much of the original string formatting probably depending on the underlying C libraries. – Ned Deily Nov 23 '10 at 05:50

score 1 · Answer 3 · answered Nov 23 '10 at 05:41

1

To continue the analogy, that size battery may not be included in the basic package, but it's easy enough to shop on-line for plug-compatible accessories:

http://code.activestate.com/recipes/365468-number-to-string-in-arbitrary-base/

answered Nov 23 '10 at 05:41

Ned Deily

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Heh, I like your analogy more :) – fmark Nov 23 '10 at 05:42

Uneven base-36 support in Python?

3 Answers3