Convert string to command..

**Adam Atlas** · Oct 18 '07, 02:55 PM

Re: Convert string to command..

On Oct 18, 10:23 am, Abandoned <best...@gmail. comwrote:

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 ?

Use the builtin function "eval".

**Diez B. Roggisch** · Oct 18 '07, 02:55 PM

Re: Convert string to command..

Abandoned wrote:

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 ?

The correct wording here would be expression. To evaluate expressions, there
is the function eval:

a = eval("['1']")

But beware: if the expression contains some potentially harmful code, it
will be executed. So it is generally considered bad style to use eval.

An example that fails would be

a = eval("10**2000* *2000")

or such thing.

Another alternative is to use parsers like simplejson to extract the
information. This of course only works, if your expressions are valid json.

Diez

**Abandoned** · Oct 18 '07, 03:15 PM

Re: Convert string to command..

Thanks you all answer..
But "eval" is very slow at very big dictionary {2:3,4:5,6:19.. ..}
(100.000 elements)
Is there any easy alternative ?

**Diez B. Roggisch** · Oct 18 '07, 03:15 PM

Re: Convert string to command..

Abandoned wrote:

Thanks you all answer..
But "eval" is very slow at very big dictionary {2:3,4:5,6:19.. ..}
(100.000 elements)
Is there any easy alternative ?

How big? How slow? For me, a 10000-element list takes 0.04 seconds to be
parsed. Which I find fast.

Diez

**Abandoned** · Oct 18 '07, 03:25 PM

Re: Convert string to command..

On Oct 18, 6:14 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Abandoned wrote:

Thanks you all answer..
But "eval" is very slow at very big dictionary {2:3,4:5,6:19.. ..}
(100.000 elements)
Is there any easy alternative ?

>
How big? How slow? For me, a 10000-element list takes 0.04 seconds to be
parsed. Which I find fast.
>
Diez

173.000 dict elements and it tooks 2.2 seconds this very big time for
my project

**Hrvoje Niksic** · Oct 18 '07, 03:35 PM

Re: Convert string to command..

Abandoned <besturk@gmail. comwrites:

173.000 dict elements and it tooks 2.2 seconds this very big time
for my project

If you're generating the string from Python, use cPickle instead.
Much faster:

>>import time
>>d = dict((i, i+1) for i in xrange(170000))
>>len(d)

170000

>>s=repr(d)
>>t0 = time.time(); d2 = eval(s); t1 = time.time()
>>t1-t0

1.5457899570465 088

>>import cPickle as pickle
>>s = pickle.dumps(d, -1)
>>len(s)

1437693

>>t0 = time.time(); d2 = pickle.loads(s) ; t1 = time.time()
>>t1-t0

0.0603079795837 40234

>>len(d2)

170000

That is 25x speedup. Note that cPickle's format is binary. Using the
textual format makes for more readable pickles, but reduces the
speedup to "only" 9.5x on my machine.

P.S.
Before someone says that using pickle is unsafe, remember that he is
considering *eval* as the alternative. :-)

**Diez B. Roggisch** · Oct 18 '07, 03:45 PM

Re: Convert string to command..

Abandoned wrote:

On Oct 18, 6:14 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

>Abandoned wrote:

Thanks you all answer..
But "eval" is very slow at very big dictionary {2:3,4:5,6:19.. ..}
(100.000 elements)
Is there any easy alternative ?

>>
>How big? How slow? For me, a 10000-element list takes 0.04 seconds to be
>parsed. Which I find fast.
>>
>Diez

>
173.000 dict elements and it tooks 2.2 seconds this very big time for
my project

Where does the data come from?

Diez

**Abandoned** · Oct 18 '07, 03:45 PM

Re: Convert string to command..

On Oct 18, 6:26 pm, Hrvoje Niksic <hnik...@xemacs .orgwrote:

Abandoned <best...@gmail. comwrites:

173.000 dict elements and it tooks 2.2 seconds this very big time
for my project

>
If you're generating the string from Python, use cPickle instead.
Much faster:
>

>import time
>d = dict((i, i+1) for i in xrange(170000))
>len(d)

170000

>s=repr(d)
>t0 = time.time(); d2 = eval(s); t1 = time.time()
>t1-t0

1.5457899570465 088

>import cPickle as pickle
>s = pickle.dumps(d, -1)
>len(s)

1437693

>t0 = time.time(); d2 = pickle.loads(s) ; t1 = time.time()
>t1-t0

>
0.0603079795837 40234>>len(d2)
>
170000
>
That is 25x speedup. Note that cPickle's format is binary. Using the
textual format makes for more readable pickles, but reduces the
speedup to "only" 9.5x on my machine.
>
P.S.
Before someone says that using pickle is unsafe, remember that he is
considering *eval* as the alternative. :-)

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 ??

**Abandoned** · Oct 18 '07, 03:55 PM

Re: Convert string to command..

On Oct 18, 6:35 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Abandoned wrote:

On Oct 18, 6:14 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Abandoned wrote:
Thanks you all answer..
But "eval" is very slow at very big dictionary {2:3,4:5,6:19.. ..}
(100.000 elements)
Is there any easy alternative ?

>

How big? How slow? For me, a 10000-element list takes 0.04 seconds to be
parsed. Which I find fast.

>

Diez

>

173.000 dict elements and it tooks 2.2 seconds this very big time for
my project

>
Where does the data come from?
>
Diez

Data come from database..
I want to cache to speed up my system and i save the dictionary to
database for speed up but eval is very slow for do this.
Not: 2.2 second only eval operation.

**Marc 'BlackJack' Rintsch** · Oct 18 '07, 03:55 PM

Re: Convert string to command..

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

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 ??

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

**Abandoned** · Oct 18 '07, 03:55 PM

Re: Convert string to command..

On Oct 18, 6:51 pm, Marc 'BlackJack' Rintsch <bj_...@gmx.net 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.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 ??

>
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..

**Diez B. Roggisch** · Oct 18 '07, 04:05 PM

Re: Convert string to command..

Abandoned wrote:

On Oct 18, 6:35 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

>Abandoned wrote:

On Oct 18, 6:14 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:
>Abandoned wrote:
Thanks you all answer..
But "eval" is very slow at very big dictionary {2:3,4:5,6:19.. ..}
(100.000 elements)
Is there any easy alternative ?

>>

>How big? How slow? For me, a 10000-element list takes 0.04 seconds to
>be parsed. Which I find fast.

>>

>Diez

>>

173.000 dict elements and it tooks 2.2 seconds this very big time for
my project

>>
>Where does the data come from?
>>
>Diez

>
Data come from database..
I want to cache to speed up my system and i save the dictionary to
database for speed up but eval is very slow for do this.
Not: 2.2 second only eval operation.

Does the dictionary change often?

And you should store a pickle to the database then. Besides, making a
database-query of that size (after all, we're talking a few megs here) will
take a while as well - so are you SURE the 2.2 seconds are a problem? Or is
it just that you think they are?

Diez

**Abandoned** · Oct 18 '07, 04:15 PM

Re: Convert string to command..

On Oct 18, 6:57 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Abandoned wrote:

On Oct 18, 6:35 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Abandoned wrote:
On Oct 18, 6:14 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:
Abandoned wrote:
Thanks you all answer..
But "eval" is very slow at very big dictionary {2:3,4:5,6:19.. ..}
(100.000 elements)
Is there any easy alternative ?

>

How big? How slow? For me, a 10000-element list takes 0.04 seconds to
be parsed. Which I find fast.

>

Diez

>

173.000 dict elements and it tooks 2.2 seconds this very big time for
my project

>

Where does the data come from?

>

Diez

>

Data come from database..
I want to cache to speed up my system and i save the dictionary to
database for speed up but eval is very slow for do this.
Not: 2.2 second only eval operation.

>
Does the dictionary change often?
>
And you should store a pickle to the database then. Besides, making a
database-query of that size (after all, we're talking a few megs here) will
take a while as well - so are you SURE the 2.2 seconds are a problem? Or is
it just that you think they are?
>
Diez- Hide quoted text -
>
- Show quoted text -

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

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

**Hrvoje Niksic** · Oct 18 '07, 04:15 PM

Re: Convert string to command..

Abandoned <besturk@gmail. comwrites:

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 ??

Because you gave it a string. If you give it a dict, you'll get a
dict:

>>import cPickle as pickle
>>a = {1:2, 3:4}
>>s = pickle.dumps(a, -1)
>>g = pickle.loads(s)
>>g

{1: 2, 3: 4}

If your existing database already has data in the "{...}" format, then
eval it only the first time. Then you'll get the dict which you can
cache thruogh the use of dumps/loads.

Convert string to command..

Convert string to command..

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