Python COM and distribution issues

[Tim Roberts]

hungjunglu at yahoo.com wrote:
>
>Thanks, but I don't think I misunderstood the GUID generation 
>mechanism. 128 bits are 128 bits, and I think you did not understand 
>that part. 128 is a finite number. It's large enough that people do 
>credit card transactions over interenet (high-encryption keys). But 
>it's a finite number. There are no magic in computers. A finite 
>number is a finite number. 

Yes, but you do not seem to grasp how incredibly large it is.  128 bits is
large enough to hold the weight of the earth in nanograms.

>As Mark Hammond mentions again and again in his book: "do not copy 
>this GUID, generate it instead by using pythoncom.CreateGuid()" OK, I 
>guess what he means is that it's OK to hard-code the GUID numbers, 
>but generate them each once using pythoncom.CreateGuid(), and then, 
>as I said before, just sit and hope for the best. 

The original GUID scheme included the 6-byte MAC ID of the generating
machine, a 4-byte date and time, and an 6-byte random number.  Assuming
that the generating machines always have an Ethernet card, it is impossible
for such a scheme to produce a duplicate.

>The chance of 
>collision (mean collision time) is probably longer than the age of 
>Solar System, but shorter than the age of the Universe. 

You are incorrect.  Do the math.  If you had been generating a billion
GUIDs per second, for every second since the big bang, you would still have
generated only one billionth of the possible GUIDs.  2^128 is unfathomably
large.
--
- Tim Roberts, timr at probo.com
  Providenza & Boekelheide, Inc.