"number-in-base" ``oneliner''
Alex Martelli
aleaxit at yahoo.com
Fri Oct 29 23:58:47 CEST 2004
I hesitate a bit to post this, but... on the Italian Python NG, somebody
was asking whether there was any way to convert an integer number x into
a string which represents it in an arbitrary base N (given a sequence
with a len of N that gives the digits to use) as "a single expression".
I haven't found a really general way, much less a clear one, but, the
best I have so far is...:
def number_in_base(x, N, digits, maxlen=99):
return '-'[x>=0:] + (
(x and ''.join([digits[k%N] for i in range(maxlen)
for k in [abs(x)//N**i] if k>0])[::-1]
) or digits[0])
Besides the lack of clarity, the obvious defect of this approach is that
darned 'maxlen' parameter -- but then, since I can have only a 'for',
not a 'while', in a list comprehension or generator expression, and I
don't think recursion qualifies as 'a single expression'...:-(
Anyway, improvements and suggestions welcome, thanks!
Alex
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