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Newsgroups: comp.lang.python
Date: Wed, 23 Jan 2013 07:30:49 -0800 (PST)
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Subject: Re: Converting a number back to it's original string (that was hashed to generate that number)
From: Ferrous Cranus <nikos.gr33k@gmail.com>
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Xref: csiph.com comp.lang.python:37483

=CE=A4=CE=B7 =CE=A4=CE=B5=CF=84=CE=AC=CF=81=CF=84=CE=B7, 23 =CE=99=CE=B1=CE=
=BD=CE=BF=CF=85=CE=B1=CF=81=CE=AF=CE=BF=CF=85 2013 3:58:45 =CE=BC.=CE=BC. U=
TC+2, =CE=BF =CF=87=CF=81=CE=AE=CF=83=CF=84=CE=B7=CF=82 Dave Angel =CE=AD=
=CE=B3=CF=81=CE=B1=CF=88=CE=B5:
> On 01/23/2013 08:38 AM, Ferrous Cranus wrote:
>=20
> > Please DON'T tell me to save both the pin <=3D> filepath and associate =
them (that can be done by SQL commands, i know)
>=20
> > I will not create any kind of primary/unique keys to the database.
>=20
> > I will not store the filepath into the database, just the number which =
indicates the filepath(html page).
>=20
> > Also no external table associating fielpaths and numbers.
>=20
> > i want this to be solved only by Python Code, not database oriented.
>=20
> >
>=20
> >
>=20
> > That is:  I need to be able to map both ways, in a one to one relation,=
 5-digit-integer <=3D> string
>=20
> >
>=20
> > int( hex ( string ) ) can encode a string to a number. Can this be deco=
ded back? I gues that can also be decoded-converted back because its not lo=
sing any information. Its encoding, not compressing.
>=20
> >
>=20
> > But it's the % modulo that breaks the forth/back association.
>=20
> >
>=20
> > So, the question is:
>=20
> >
>=20
> > HOW to map both ways, in a one to one relation, (5-digit-integer <=3D> =
string) without losing any information?
>=20
> >
>=20
>=20
>=20
> Simple.  Predefine the 100,000 legal strings, and don't let the user use=
=20
>=20
> anything else.  One way to do that would be to require a path string of=
=20
>=20
> no more than 5 characters, and require them all to be of a restricted=20
>=20
> alphabet of 10 characters.  (eg. the alphabet could be 0-9, which is=20
>=20
> obvious, or it could be ".aehilmpst" (no uppercase, no underscore, no=20
>=20
> digits, no non-ascii, etc.)
>=20
>=20
>=20
> In the realistic case of file paths or URLs, it CANNOT be done.

OK, its not doable. I'll stop asking for it.
CHANGE of plans.
i will use the database solution which is the most easy wau to do it:

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

	# insert new page record in table counters or update it if already exists
	try:
		cursor.execute( '''INSERT INTO counters(page, hits) VALUES(%s, %s)=20
								ON DUPLICATE KEY UPDATE hits =3D hits + 1''', (htmlpage, 1) )
	except MySQLdb.Error, e:
		print ( "Query Error: ", sys.exc_info()[1].excepinfo()[2] )
	=09
	# update existing visitor record if same pin and same host found
	try:
		cursor.execute( '''UPDATE visitors SET hits =3D hits + 1, useros =3D %s, =
browser =3D %s, date =3D %s WHERE pin =3D %s AND host =3D %s''', (useros, b=
rowser, date, page, host))
	except MySQLdb.Error, e:
		print ( "Error %d: %s" % (e.args[0], e.args[1]) )
=09
	# insert new visitor record if above update did not affect a row
	if cursor.rowcount =3D=3D 0:
		cursor.execute( '''INSERT INTO visitors(hits, host, useros, browser, date=
) VALUES(%s, %s, %s, %s, %s)''', (1, host, useros, browser, date) )

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

I can INSERT a row to the table "counter"
I cannot UPDATE or INSERT into the table "visitors" without knowing the "pi=
n" primary key number the database created.

Can you help on this please?