Pickling a dictionary into a PostgreSQL database?
teth
article.rating = article.rating + 1
ratings[request.user.username] = 1
article.rating_list = pickle.dumps(ratings)
article.save()
ratings looks like this:
{'froob': 1, 'alik': 1, 'teth': 1}
When I try and load the pickled string from the database it gives me
the following error:
KeyError at /article/testing123/up/
'\x00'
article/testing123 loads the article testing123 from the database and
the /up/ is to improve the rating of it. The dictionary is to prevent
users from rating the same article twice by putting their username as
an index in a dictionary. What am I doing wrong? (The pickled string
is stored in a TEXT field)
Dj Gilcrease
create a ArticleVote models, something like
http://dpaste.com/hold/109437/
I also show how I would use it in the views
Dj Gilcrease
OpenRPG Developer
~~http://www.openrpg.com
bruno desthuilliers
> Hello, I pickled a dictionary and stored it in my database like this:
> article.rating = article.rating + 1
> ratings[request.user.username] = 1
> article.rating_list = pickle.dumps(ratings)
> article.save()
>
> ratings looks like this:
> {'froob': 1, 'alik': 1, 'teth': 1}
>
> When I try and load the pickled string from the database it gives me
> the following error:
> KeyError at /article/testing123/up/
> '\x00'
code that raises looks like, and what does the field content looks
like ?
> article/testing123 loads the article testing123 from the database and
> the /up/ is to improve the rating of it. The dictionary is to prevent
> users from rating the same article twice by putting their username as
> an index in a dictionary. What am I doing wrong?
storing a serialized dict into a db field, instead of properly using a
item/user table. But I guess this is not the answer you expect !-)
> (The pickled string
> is stored in a TEXT field)
Sorry, not really helpful, I'm afraid.
Torsten Bronger
teth writes:
> [...]
>
> When I try and load the pickled string from the database it gives me
> the following error:
> KeyError at /article/testing123/up/
> '\x00'
I do the same thing, and I remember that I was forced to write
"pickle.loads(str(database_text))" (note the str()). However, I
don't remember the exception I was confronted with.
Tschö,
Torsten.
--
Torsten Bronger, aquisgrana, europa vetus
Jabber ID: torsten...@jabber.rwth-aachen.de
teth
The reason I use a dict instead of a list is because I can add an
entry that does not come in numeric order (with a list you cannot add
an item to it simply by list[32] if the list is not that long).
I used a dict because it is very fast to run if rating['froob'] == 1.
Also it simplifies the database models.
On Jan 15, 1:00 pm, Torsten Bronger <bron...@physik.rwth-aachen.de>
wrote:
> Hallöchen!
>
> teth writes:
> > [...]
>
> > When I try and load the pickled string from thedatabaseit gives me
> > KeyError at /article/testing123/up/
> > '\x00'
>
> I do the same thing, and I remember that I was forced to write
> "pickle.loads(str(database_text))" (note the str()). However, I
> don't remember the exception I was confronted with.
>
> Tschö,
> Torsten.
>
> --
> Torsten Bronger, aquisgrana, europa vetus
Torsten Bronger
teth writes:
> Using str(pickle.dumps()) and the pickle.loads(str()) works
> perfectly.
Unfortunately, I had to realise that it is not so simple due to
<http://bugs.python.org/issue2980>. Now it use the following
functions:
def ascii_pickle(python_object):
u"""Converts an arbitrary Python object to an ASCII-only string to be
written to the database. Unfortunately, even protocol 0 of Python's
``pickle`` module may emit non-ASCII characters, see
<http://bugs.python.org/issue2980>. However, this is dangerous since the
database expects Unicode strings and can't decode such octet strings.
Therefore, this routine does another encoding step using base64. This
makes debugging slightly more difficult, but there we go.
:Parameters:
- `python_object`: the object instance to be pickled
:type python_object: object
:Return:
the ASCII-only string representing the object instance
:rtype: str
"""
# FixMe: Maybe instead of base64 another encoder should be used that keeps
# the string largely readable.
return base64.b64encode(pickle.dumps(python_object, protocol=2))
def ascii_unpickle(string):
u"""This is the inverse function of `ascii_pickle`.
:Parameters:
- `string`: the ASCII-only database string to be unpickled
:type string: str
:Return:
the original Python object instance that was represented by the string
:rtype: object
"""
return pickle.loads(base64.b64decode(string))
Tschö,
Torsten.
--
Torsten Bronger, aquisgrana, europa vetus
Jabber ID: torsten...@jabber.rwth-aachen.de
teth
problem which I think may have been solved by this post. I used
urlsafe_b64encode() and urlsafe_b64decode because a URL cannot contain
any non-ASCII characters (can it?). I could also have used the normal
b64 functions, but I wanted to be sure.
On Jan 21, 10:07 am, Torsten Bronger <bron...@physik.rwth-aachen.de>
wrote:
> Hallöchen!
>
> teth writes:
> > Using str(pickle.dumps()) and thepickle.loads(str()) works
>
> Unfortunately, I had to realise that it is not so simple due to
> <http://bugs.python.org/issue2980>. Now it use the following
> functions:
>
> def ascii_pickle(python_object):
> u"""Converts an arbitrary Python object to an ASCII-only string to be
> <http://bugs.python.org/issue2980>. However, this is dangerous since the
> makes debugging slightly more difficult, but there we go.
>
> :Parameters:
> - `python_object`: the object instance to be pickled
>
> :type python_object: object
>
> :Return:
> the ASCII-only string representing the object instance
>
> :rtype: str
> """
> # FixMe: Maybe instead of base64 another encoder should be used that keeps
> # the string largely readable.
> return base64.b64encode(pickle.dumps(python_object, protocol=2))
>
> def ascii_unpickle(string):
> u"""This is the inverse function of `ascii_pickle`.
>
> :Parameters:
> :type string: str
>
> :Return:
> the original Python object instance that was represented by the string
>
> :rtype: object
> """
> returnpickle.loads(base64.b64decode(string))
>
> Tschö,
> Torsten.
>
> --
> Torsten Bronger, aquisgrana, europa vetus