Convert string to command..

[Abandoned]

I want to convert a string to command..
For example i have a string:
a="['1']"
I want to do this list..
How can i do ?

[Sebastian Bassi]

On 10/18/07, Adam Atlas <ad**@atlas.stw rote:

>
Use the builtin function "eval".

What is the difference with os.system()?

--
Sebastián Bassi (ã‚»ãƒ�ステ゠£ã‚¢ãƒ³). Diplomado en Ciencia y TecnologÃ*a.
Curso Biologia molecular para programadores: http://tinyurl.com/2vv8w6
GPG Fingerprint: 9470 0980 620D ABFC BE63 A4A4 A3DE C97D 8422 D43D

[Richard Brodie]

"Matimus" <mc******@gmail .comwrote in message
news:11******** **************@ q5g2000prf.goog legroups.com...

I think several people have given you the correct answer, but for some
reason you aren't getting it. Instead of saving the string
representation of a dictionary to the database...

Mind you, if this were Jeopardy, "Store a binary pickle
of a denormalized table back in the database" would
be a tough one.

[Bruno Desthuilliers]

Abandoned a écrit :

On Oct 18, 6:51 pm, Marc 'BlackJack' Rintsch <[e-mail] wrote:

>On Thu, 18 Oct 2007 08:41:30 -0700, Abandoned wrote:

>>import cPickle as pickle
a="{2:3,4:6,2 :7}"
s=pickle.dump s(a, -1)
g=pickle.load s(s);
print g
'{2:3,4:6,2:7 }'
Thank you very much for your answer but result is a string ??

In Python terms yes, strings in Python can contain any byte value. If you
want to put this into a database you need a BLOB column or encode it as
base64 or something similar more ASCII safe.

Ciao,
Marc 'BlackJack' Rintsch

'{2:3,4:6,2:7}' already in database, i select this and convert to real
dictionary..

MVHO is that whoever uses a RDBMS to store language-specific serialized
collections should be shot down without sommation.

[Bruno Desthuilliers]

Abandoned a écrit :
(snip)

import cPickle as pickle
a="{2:3,4:6,2:7 }"
s=pickle.dumps( a, -1)
g=pickle.loads( s);
print g
'{2:3,4:6,2:7}'

Thank you very much for your answer but result is a string ??

Of course it's a string. That's what you pickled. What did you hope ? If
you want a dict back, then pickle a dict.

[Bruno Desthuilliers]

Richard Brodie a écrit :

"Matimus" <mc******@gmail .comwrote in message
news:11******** **************@ q5g2000prf.goog legroups.com...

>I think several people have given you the correct answer, but for some
reason you aren't getting it. Instead of saving the string
representati on of a dictionary to the database...

Mind you, if this were Jeopardy, "Store a binary pickle
of a denormalized table back in the database" would
be a tough one.

Indeed.

[Bruno Desthuilliers]

Abandoned a écrit :
(snip)

I'm very confused :(
I try to explain main problem...
I have a table like this:
id-1 | id-2 | value
23 24 34
56 68 66
56 98 32455
55 62 655
56 28 123
.... ( 3 millions elements)

I select where id=56 and 100.000 rows are selecting but this took 2
second. (very big for my project)

Not to bad in the absolute.

I try cache to speed up this select operation..
And create a cache table:
id-1 | all
56 {68:66, 98:32455, 62:655}

I really doubt this is the right way to go.

When i select where id 56 i select 1 row and its took 0.09 second but
i must convert text to dictionary..

Have you got any idea what can i do this conver operation ?

Other alread answered

Have you got any idea what can i do cache for this table ?

Depends on your RDBMS. And as far as I'm concerned, I'd start by trying
to find out how to optimize this query within the RDBMS - good ones are
usually highly optimized softwares with provision for quite a lot of
performance tuning.

[Hrvoje Niksic]

Abandoned <be*****@gmail. comwrites:

When you load it, convert the string to dict with cPickle.loads
instead of with eval.

Yes i understand and this very very good ;)

Good! :-)

psycopg2.Progra mmingError: invalid byte sequence for encoding "UTF8":
0x80
HINT: This error can also happen if the byte sequence does not match
the encoding expected by the server, which is controlled by
"client_encodin g".

Use a different column type for cache2's column, one more appropriate
for storing binary characters (perhaps BYTEA for Postgres). Don't
forget to also use a bind variable, something like:

cursor.execute( "INSERT INTO cache2 VALUES (?)", a)

Using "INSERT ... ('%s')" % (a) won't work, since the huge binary
string in a can contain arbitrary characters, including the single
quote.

[Carsten Haese]

On Thu, 2007-10-18 at 19:53 +0200, Hrvoje Niksic wrote:

Don't
forget to also use a bind variable, something like:

cursor.execute( "INSERT INTO cache2 VALUES (?)", a)

I second the advice, but that code won't work. The bind parameters must
be a sequence, and psycopg2 (unfortunately) uses %s for parameter
markers, instead of the SQL standard question mark. So the actual code
would be

cursor.execute( "INSERT INTO cache2 VALUES (%s)", (a,) )

HTH,

--
Carsten Haese
http://informixdb.sourceforge.net

[sjdevnull]

On Oct 18, 1:38 pm, Bruno Desthuilliers <bruno.
42.desthuilli.. [e-mail] ro.oops.comwrot e:

Abandoned a écrit :
(snip)

I'm very confused :(
I try to explain main problem...
I have a table like this:
id-1 | id-2 | value
23 24 34
56 68 66
56 98 32455
55 62 655
56 28 123
.... ( 3 millions elements)

I select where id=56 and 100.000 rows are selecting but this took 2
second. (very big for my project)

Not to bad in the absolute.

I try cache to speed up this select operation..
And create a cache table:
id-1 | all
56 {68:66, 98:32455, 62:655}

I really doubt this is the right way to go.

When i select where id 56 i select 1 row and its took 0.09 second but
i must convert text to dictionary..

Have you got any idea what can i do this conver operation ?

Other alread answered

Have you got any idea what can i do cache for this table ?

Depends on your RDBMS. And as far as I'm concerned, I'd start by trying
to find out how to optimize this query within the RDBMS - good ones are
usually highly optimized softwares with provision for quite a lot of
performance tuning.

Just the overhead of the query is a killer compared to a dictionary
lookup in Python, even if all you're doing is selecting an integer
from a 1-row, 1-column table.

Usually you can get around that by making a single query to return all
of your results (or a handful of queries), but occasionally it just
doesn't matter how fast the DB can get to the data--the simple act of
asking it is slow enough on its own.

[Steven D'Aprano]

On Thu, 18 Oct 2007 14:05:34 -0300, Sebastian Bassi wrote:

On 10/18/07, Adam Atlas <ad**@atlas.stw rote:

>>
Use the builtin function "eval".

What is the difference with os.system()?

Everything.

eval() evaluates Python expressions like "x.append(2+3)" .

os.system() calls your operating system's shell with a command.
--
Steven.