Re: [web2py] Re: db query not working
On 11 Jul 2012, at 8:03 AM, hasan alnator wrote:
> Where ??
In the DAL chapter, toward the end of the "Logical operators" section.
http://web2py.com/books/default/chapter/29/6#Logical-operators
>
> On Wed, Jul 11, 2012 at 6:00 PM, Jonathan Lundell wrote:
> On 11 Jul 2012, at 7:25 AM, Jonathan Lundell wrote:
> >
> > On 11 Jul 2012, at 7:19 AM, hasan alnator wrote:
> >> ohh thank you Jonathan its working now , but can you tell me why ? i dont
> >> understand
> >
> > web2py overloads & to perform a logical-and role here, but it can't alter
> > Python's operator precedence. The & operator has higher precedence than ==,
> > unlike the 'and' operator (or the '&&' operator in C). So this:
> >
> > video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher ==
> > "xx").select(db.Videos.ALL)
> >
> > evaluates the same as this:
> >
> > video = db(db.Videos.Video_Type == ("XXX" & db.Videos.Teacher) ==
> > "xx").select(db.Videos.ALL)
>
> I added a line to the book pointing this out.
>
Re: [web2py] Re: db query not working
Where ??
On Wed, Jul 11, 2012 at 6:00 PM, Jonathan Lundell wrote:
> On 11 Jul 2012, at 7:25 AM, Jonathan Lundell wrote:
> >
> > On 11 Jul 2012, at 7:19 AM, hasan alnator wrote:
> >> ohh thank you Jonathan its working now , but can you tell me why ? i
> dont understand
> >
> > web2py overloads & to perform a logical-and role here, but it can't
> alter Python's operator precedence. The & operator has higher precedence
> than ==, unlike the 'and' operator (or the '&&' operator in C). So this:
> >
> > video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher ==
> "xx").select(db.Videos.ALL)
> >
> > evaluates the same as this:
> >
> > video = db(db.Videos.Video_Type == ("XXX" & db.Videos.Teacher) ==
> "xx").select(db.Videos.ALL)
>
> I added a line to the book pointing this out.
>
> >
> >
> >>
> >> On Wed, Jul 11, 2012 at 5:14 PM, Jonathan Lundell
> wrote:
> >> On 11 Jul 2012, at 7:09 AM, hasan alnator wrote:
> >>> Dear David,
> >>>
> >>> the '&' is not supported when i use it i get this :
> >>>
> >>> unsupported operand type(s) for &: 'str' and 'Field'
> >>>
> >>
> >> video = db((db.Videos.Video_Type == "XXX") & (db.Videos.Teacher ==
> "xx")).select(db.Videos.ALL)
> >>
> >>
> >>> On Wed, Jul 11, 2012 at 1:41 PM, David Marko
> wrote:
> >>> Should not this ...
> >>> video = db(db.Videos.Video_Type == "XXX" and db.Videos.Teacher ==
> "xx").select(db.Videos.ALL)
> >>>
> >>> be rather like this? (see and vs. &)
> >>> video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher ==
> "xx").select(db.Videos.ALL)
> >
>
>
>
Re: [web2py] Re: db query not working
On 11 Jul 2012, at 7:25 AM, Jonathan Lundell wrote:
>
> On 11 Jul 2012, at 7:19 AM, hasan alnator wrote:
>> ohh thank you Jonathan its working now , but can you tell me why ? i dont
>> understand
>
> web2py overloads & to perform a logical-and role here, but it can't alter
> Python's operator precedence. The & operator has higher precedence than ==,
> unlike the 'and' operator (or the '&&' operator in C). So this:
>
> video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher ==
> "xx").select(db.Videos.ALL)
>
> evaluates the same as this:
>
> video = db(db.Videos.Video_Type == ("XXX" & db.Videos.Teacher) ==
> "xx").select(db.Videos.ALL)
I added a line to the book pointing this out.
>
>
>>
>> On Wed, Jul 11, 2012 at 5:14 PM, Jonathan Lundell wrote:
>> On 11 Jul 2012, at 7:09 AM, hasan alnator wrote:
>>> Dear David,
>>>
>>> the '&' is not supported when i use it i get this :
>>>
>>> unsupported operand type(s) for &: 'str' and 'Field'
>>>
>>
>> video = db((db.Videos.Video_Type == "XXX") & (db.Videos.Teacher ==
>> "xx")).select(db.Videos.ALL)
>>
>>
>>> On Wed, Jul 11, 2012 at 1:41 PM, David Marko wrote:
>>> Should not this ...
>>> video = db(db.Videos.Video_Type == "XXX" and db.Videos.Teacher ==
>>> "xx").select(db.Videos.ALL)
>>>
>>> be rather like this? (see and vs. &)
>>> video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher ==
>>> "xx").select(db.Videos.ALL)
>
Re: [web2py] Re: db query not working
On 11 Jul 2012, at 7:19 AM, hasan alnator wrote:
> ohh thank you Jonathan its working now , but can you tell me why ? i dont
> understand
web2py overloads & to perform a logical-and role here, but it can't alter
Python's operator precedence. The & operator has higher precedence than ==,
unlike the 'and' operator (or the '&&' operator in C). So this:
video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher ==
"xx").select(db.Videos.ALL)
evaluates the same as this:
video = db(db.Videos.Video_Type == ("XXX" & db.Videos.Teacher) ==
"xx").select(db.Videos.ALL)
>
> On Wed, Jul 11, 2012 at 5:14 PM, Jonathan Lundell wrote:
> On 11 Jul 2012, at 7:09 AM, hasan alnator wrote:
>> Dear David,
>>
>> the '&' is not supported when i use it i get this :
>>
>> unsupported operand type(s) for &: 'str' and 'Field'
>>
>
> video = db((db.Videos.Video_Type == "XXX") & (db.Videos.Teacher ==
> "xx")).select(db.Videos.ALL)
>
>
>> On Wed, Jul 11, 2012 at 1:41 PM, David Marko wrote:
>> Should not this ...
>> video = db(db.Videos.Video_Type == "XXX" and db.Videos.Teacher ==
>> "xx").select(db.Videos.ALL)
>>
>> be rather like this? (see and vs. &)
>> video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher ==
>> "xx").select(db.Videos.ALL)
>
Re: [web2py] Re: db query not working
ohh thank you Jonathan its working now , but can you tell me why ? i dont understand On Wed, Jul 11, 2012 at 5:14 PM, Jonathan Lundell wrote: > On 11 Jul 2012, at 7:09 AM, hasan alnator wrote: > > Dear David, > > the '&' is not supported when i use it i get this : > > unsupported operand type(s) for &: 'str' and 'Field' > > > video = db((db.Videos.Video_Type == "XXX") & (db.Videos.Teacher == > "xx")).select(db.Videos.ALL) > > > On Wed, Jul 11, 2012 at 1:41 PM, David Marko wrote: > >> Should not this ... >> video = db(db.Videos.Video_Type == "XXX" and db.Videos.Teacher == >> "xx").select(db.Videos.ALL) >> >> be rather like this? (see and vs. &) >> video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher == >> "xx").select(db.Videos.ALL) >> > > > >
Re: [web2py] Re: db query not working
On 11 Jul 2012, at 7:09 AM, hasan alnator wrote: > Dear David, > > the '&' is not supported when i use it i get this : > > unsupported operand type(s) for &: 'str' and 'Field' > video = db((db.Videos.Video_Type == "XXX") & (db.Videos.Teacher == "xx")).select(db.Videos.ALL) > On Wed, Jul 11, 2012 at 1:41 PM, David Marko wrote: > Should not this ... > video = db(db.Videos.Video_Type == "XXX" and db.Videos.Teacher == > "xx").select(db.Videos.ALL) > > be rather like this? (see and vs. &) > video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher == > "xx").select(db.Videos.ALL) >
Re: [web2py] Re: db query not working
Dear David, the '&' is not supported when i use it i get this : unsupported operand type(s) for &: 'str' and 'Field' On Wed, Jul 11, 2012 at 1:41 PM, David Marko wrote: > Should not this ... > video = db(db.Videos.Video_Type == "XXX" and db.Videos.Teacher == > "xx").select(db.Videos.ALL) > > be rather like this? (see and vs. &) > video = db(db.Videos.Video_Type == "XXX" & db.Videos.Teacher == > "xx").select(db.Videos.ALL) >
