On 8 Sep 2013, at 02:36, Mohsen Pahlevanzadeh m.pahlevanza...@gmail.com wrote:
Suppose i need to send a set of table field and a value to search, i found
the following code:
///
q = session.query(myClass)
for attr, value in web_dict.items():
q
= q.filter(getattr(myClass, attr).like(%%%s%% % value))
///
But it have problem,
i'm newbie in python can you investigate it?
I'm not sure if you understand how the above code is supposed to work, so I'll
explain it. It assumes that web_dict is a dictionary mapping names of
attributes of myClass to strings, and it will return instances of myClass where
all the named attributes contain those values as substrings.
So, for example, if myClass had name and phonenumber properties, and
assuming that web_dict looks like this:
web_dict = {
'name': 'Mohsen',
'phonenumber': '1',
}
web_dict.items() returns a list like this:
[('name', 'Mohsen'), ('phonenumber', '1')]
So the first time round the for loop, attr will be set to name and
value will be Mohsen. The second time round, attr will be phonenumber
and value will be 1.
(Note that dictionaries aren't ordered, so web_dict.items() could actually
return the pairs in a different order)
Let's break the loop down into a few more lines:
for attr, value in web_dict.items():
column = getattr(myClass, attr)
condition = column.like('%%%s%%' % value)
q = q.filter(condition)
getattr is a python function that retrieves a named attribute from an object.
So:
getattr(myClass, phonenumber)
is exactly equivalent to:
myClass.phonenumber
So the first time round the loop, getattr(myClass, attr) returns
myClass.name, and the second time round it will return myClass.phonenumber.
(http://docs.python.org/2/library/functions.html#getattr)
'%%%s%%' % value is a python string-formatting function. %s will be
replaced by whatever is in value, and %% becomes %. So in our example
above, the first time round the loop we will have the string %Mohsen%' and the
second time round it will be %1%.
(http://docs.python.org/2/library/stdtypes.html#string-formatting)
That string is passed to the column.like function, which produces SQL such as
'name LIKE %Mohsen%'. That condition is then passed to Query.filter, which
will add it to the WHERE clause of the SQL using AND.
So the code will eventually end up doing something like this:
q = session.query(myClass)
q = q.filter(myClass.name.like('%Mohsen%'))
q = q.filter(myClass.phonenumber.like('%1%'))
which will end up producing SQL something like:
SELECT myClass columns
FROM myClass table
WHERE name LIKE '%Mohsen%'
AND phonenumber LIKE '%1%'
Is that the sort of SQL that you are hoping to see, or do you need something
different?
Simon
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