Il 28/03/2014 14:53, Peter Otten ha scritto:
Daniele Forghieri wrote:
Il 28/03/2014 10:16, Peter Otten ha scritto:
Daniele Forghieri wrote:
Hi to all. I'm using sqlite3 with python 2.7 on windows.
I use the query substitution parameters in my query but I need to pass
part of the query to a function, something like (it's not the real
examples, just to clarify the question):
def loadAll(cursor, id, queryAdd = None):
if queryAdd is None:
qry = 'select * from files where catalog = ?'
else:
qry = 'select * from files where catalog = ? and %s' %
(queryAdd))
cursor.execute(qry, (id, ))
...
I would like to use the query substitution even when I create, in
another piece of code, the queryAdd part, something like:
queryAdd = cursor.querySubst('enabled = ? and hide = ? and data > ?',
(enabled, hidden, min_date, ))
when the function take care of the date format, quoting the parameter
and so on
It's possible or not ?
You can use named parameters
http://docs.python.org/dev/library/sqlite3.html#cursor-objects
Your function might become (untested)
def load_all(cursor, parameters, condition="catalog = :id"):
query = 'select * from files where ' + condition
cursor.execute(query, parameters)
...
load_all(
cursor, dict(id=42, fromdate=datetime.date.today()),
condition="catalog = :id and date >= :fromdate")
Thank. With this I can solve the problem but I have to specify the
query twice and if I have to change something I need to made it
everywhere I use the function and is something I would like to avoid.
How about that one:
def query_subst(sql, parameters):
return sql, parameters
def load_all(cursor, id, query_add=None):
query = 'select * from files where catalog = ?'
parameters = (id,)
if query_add is not None:
query += " and " + query_add[0]
parameters += query_add[1]
cursor.execute(query, parameters)
...
enabled = True
hidden = False
min_date = datetime.date.today()
query_add = query_subst(
'enabled = ? and hide = ? and date > ?',
(enabled, hidden, min_date))
load_all(cs, 42, query_add)
This one is, IMHO, cleaner and more manageable!
Thank you very very much, I really appreciate your help.
I also don't like very mush to pass or create a dict for a function
call but that's probably me coming from old plain C ;)
Get over it ;)
I'm trying but the old habits comes out, the first time I need
to parse a string I do it like in C, looking at every single char using
a couple of help function: the performance were really horrible, the
memory used was huge than I change the way I do things (and start to use
sqlite3 to store my data instead of using text files, parsed by a
proprietary lib).
The worse is the contrary, when I must use C and I think 'Here
I use a dictionary, at the end convert it in a list that I sort with
that key ...' only to realize that I don't have dictionary and the list
I can use are very less manageable that the ones I used in Python ...
It seems to me that going from C to Python you start writing
inefficient code or write more lines than an average Python programmer
but 'something moves' and the result happens. Moving from Python to C I
always feel like I missed something and the first approach, good for
Python, is simply not working in C ;(
Thanks again
Daniele Forghieri
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