[Python-ideas] Add a builtin method to 'int' for base/radix conversion

Masklinn masklinn at masklinn.net
Mon Aug 31 15:58:53 CEST 2009

On 31 Aug 2009, at 15:00 , Nick Coghlan wrote:
Yuvgoog Greenle wrote:
>> I believe int(s, base) needs an inverse function to allow string
>> representation with different bases. An example use case is  
>> 'hashing' a
>> counter like video ID's on youtube, you could use a regular int
>> internally and publish a shorter base-62 id
>> for links.
>> This subject was discussed 2.5 years ago:
>> http://mail.python.org/pipermail/python-dev/2006-January/059789.html
>> I opened a feature request ticket:
>> http://bugs.python.org/issue6783
>> Some of the questions that remain:
>> 1. Whether this should be a method for int or a regular function in a
>> standard library module like math.
>> 2. What should the method/function be called? (base_convert, radix,  
>> etc)
>> What do you guys think?
> This has been coming up for years and always gets bogged down in a
> spelling argument (a method on int, a function in the math module  
> and an
> update to the str.format mini language would be the current  
> contenders).
> However, most of the actual real use cases for bases between 2 and 36
> were dealt with by the addition of binary and octal output to string
> formatting so the impetus to do anything about it is now a lot lower.
> As far as bases between 37 and 62 go, that would involve first getting
> agreement on extending int() to handle those bases by allowing case
> sensitive digit parsing. Presumably that would use string lexical
> ordering so that int('a', 37) > int('A', 37) and int('b', 37) would
> raise an exception.
> That would only be intuitive to someone that knows how ASCII based
> alphanumeric ordering works though.
Or it could be handled via a translation table (needed both ways of  
course) mapping n indexes to n characters (with n the base you're  
working with), defaulting to something sane.

Though I'm not sure this is of much interest really: even Erlang  
(which provides pretty good base conversion tools: it supports literal  
integers of any base between 2 and 36) doesn't natively support bases  
beyond 36. A library would probably be better for those more  
conflictual (or less intuitive) ranges.

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