Re: [google-appengine] Hash function

[Jeff Schnitzer]

Alternatively, just use the id generator. Personally I use the id generator
and crockford's base32 encoding variant to generate "pretty" (that is,
short enough to type or read over phone if necessary) ids for public URLs.

Jeff

On Wed, May 27, 2015 at 7:55 AM, Karl MacMillan  wrote:

>
>  On May 27, 2015, at 10:50 AM, Saturnino Mateus 
> wrote:
>
> Hello! I need to create a page to tracking orders, each order must have a
> key. How can i generate this key? Im thinking use hash, is there any good
> hash function without colision? Is there other way to solve it with GAE?
>
>
> This isn’t exactly GAE specific, but you probably want a UUID:
>
> https://docs.oracle.com/javase/7/docs/api/java/util/UUID.html
>  https://docs.python.org/2/library/uuid.html
>
> Karl
>
>  Regards
>
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Re: [google-appengine] Hash function

[Karl MacMillan]

  

> On May 27, 2015, at 10:50 AM, Saturnino Mateus  wrote:
> 
> 
> Hello! I need to create a page to tracking orders, each order must have a 
> key. How can i generate this key? Im thinking use hash, is there any good 
> hash function without colision? Is there other way to solve it with GAE?
> 
> 
> 

This isn’t exactly GAE specific, but you probably want a UUID:


https://docs.oracle.com/javase/7/docs/api/java/util/UUID.html

https://docs.python.org/2/library/uuid.html



Karl


> Regards
> 
> 
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> 

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[google-appengine] Hash function

[Saturnino Mateus]

Hello! I need to create a page to tracking orders, each order must have a key. 
How can i generate this key? Im thinking use hash, is there any good hash 
function without colision? Is there other way to solve it with GAE?

Regards

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[google-appengine] Hash function: migrating from Python 2.5 to Python 2.7

[Andrin von Rechenberg]

The built-in hash function differs from Python2.5 to Python2.7.

If you are planning to migrate from Python 2.5 to Python 2.7 and
you were dumb enough to store the value of python 2.5's hash
function, just like I did, you might be interested in the following
code snippet.

This is the hash function that Google uses in production for python 2.5:

def c_mul(a, b):

  return eval(hex((long(a) * b) & 0xL)[:-1])

def py25hash(self):

  if not self:

return 0 # empty

  value = ord(self[0]) << 7

  for char in self:

value = c_mul(103, value) ^ ord(char)

  value = value ^ len(self)

  if value == -1:

value = -2

  return value


I wonder why Google is not using 64bit hashes in Python 2.7

Cheers,
-Andrin

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