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Date: Tue, 22 Jan 2013 15:43:27 -0500
From: Dave Angel <d@davea.name>
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To: python-list@python.org
Subject: Re: Converting a string to a number by using INT  (no hash method)
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On 01/22/2013 03:30 PM, Leonard, Arah wrote:
>> The perl code will produce the same hash for  "abc.html" as for "bca.html"  That's probably one reason Leonard didn't try to transliterate the buggy code.
>>
>
> Actually, to give credit where it's due, it wasn't me.  I just modified someone else's interesting solution in this thread and added the silly limit of 10000 to it.
>

That's okay.  The OP doesn't seem to know anything about programming, or 
about information theory, so the fact you gave a single line that 
actually "works" must be extraordinarily valuable to him.  When he was 
trying to use the md5 module, I gave him the hints about his five 
programming errors, and was about to expand on it when i noticed his 4 
digit limitation.

>> In any case, the likelihood of a hash collision for any non-trivial website is substantial.
>>
>
> Exactly.  Four digits is hardly enough range for it to be even remotely safe.  And even then range isn't really the issue as technically it just improves your odds.
>
> The results of a modulus operator are still non-unique no matter how many digits are there to work with ... within reason.  Statistically anyone who buys a ticket could potentially win the lottery no matter how bad the odds are.  ;)
>
> And now back to the OP, I'm still confused on this four-digit limitation.  Why isn't the limitation at least adhering to a bytelength like byte/short/long?  Is this database storing a string of characters instead of an actual number?  (And if so, then why not just block out 255 characters instead of 4 to store a whole path?  Or at the very least treat 4 characters as 4 bytes to greatly increase the numeric range?)
>

I wish I had done the internet search earlier.  This name 'ferrous 
cranus' is a pseudonym of various trolls, and anybody who'd adopt it 
isn't worth our time.

Thanks to Alan Spence for spotting that.  I'll plonk 'ferrous cranus' now.


-- 
DaveA