Writing a string.ishex function

[MRAB]

D'Arcy J.M. Cain wrote:
> On Thu, 14 Jan 2010 07:52:58 -0800 (PST)
> chandra <chyavana at gmail.com> wrote:
>> Folks,
>>
>> I am new to Python and could not find a function along the lines of
> 
> Welcome.
> 
>> string.ishex in Python. There is however, a string.hexdigits constant
>> in the string module. I thought I would enhance the existing modlue
>> but am unsure how I should go about it. Specifically, I have attempted
>> this much:
> 
> You should always test code before posting and post the exact code that
> you tested.
> 
>> ---cut---
>> #! /usr/bin/python
>> # -*- coding: utf-8 -*-
>>
>> import string
>>
>> def ishex(string):
> 
> Bad idea to name your variable after a module.  This function fails
> because of that.
> 
>>     ishex = False
>>     for i in strdef ishex(sing:
>>         if i in string.hexdigits:
>>             ishex = True
>>         else:
>>             ishex = False
>>             break
>>     return ishex
> 
> After renaming the variable this works but you can simplify it.
> 
> 
>> ---cut---
> 
> Just return False once you find a non-hex digit.
> 
> def ishex(s):
>   for c in s:
>     if not c in string.hexdigits: return False
> 
>   return True
> 
> And here are your unit tests.  Every line should print "True".
> 
> print ishex('123') is True
> print ishex('abc') is True
> print ishex('xyz') is False
> print ishex('0123456789abcdefABCDEF') is True
> print ishex('0123456789abcdefABCDEFG') is False
> 
Don't use 'is', use '=='.

BTW, ishex('') should return False.