[Python-3000] Fwd: Re: Fwd: Re: Fwd: Re: Octal (original) (raw)

Guido van Rossum guido at python.org
Sat Mar 17 16:22:24 CET 2007

On 3/16/07, Patrick Maupin <pmaupin at gmail.com> wrote:

Hexadecimal numbers traditionally support upper- and lower-case display, chosen by the case of the 'x' character. Python supports this both for input and display, and probably needs to continue to support the option of upper or lowercase hex for display.

I think perhaps it should be supported for input, as well, both to have symmetry with the display, and to allow for easy cut and paste (and eval() and int(s, 0)) of hexadecimal numbers from other sources. Obviously, we cannot support this easy eval() or int(s, 0) for octal in the future, but arguably, there are a lot more hexadecimal numbers of either case "in the wild" than there are octal numbers. I understand that the proposal is to allow 0xabc or 0xABC, but not allow 0Xabc or 0XABC, but one of the strengths of Python is that I can easily parse files containing numerical data from almost arbitrary sources, and this may be a case where "practicality beats purity" should rule, although it may also be an easy counterargument that I/O symmetry is not really that important, and that one can easily write "x = x.replace('0X', '0x')" for the example I have given. Your call.

I'll take your word that 0X is popular for data files out there. I think I would support that in int(s, 0) but not in eval(s) -- IOW, hex literals in Python source code must start with 0x. After that they can use ABC or abc or AbC for all I care. I used Google's code search to find occurrences of 0X followed by a hex digit (and not preceded by a word character) and found only very few hits, many of which were false positives (e.g. in Python's own test suite there are a bunch of occurrences in string literals verifying that %#X produces the right output).

Since this is trivial for the conversion tool, I'm not worried about breaking that code at all.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

More information about the Python-3000 mailing list