[web2py] Re: dynamic keywords on database update

[Wikus van de Merwe]

You can pass a dictionary to a function as if you are passing keyword 
arguments.
kwargs = {"a":1, "b":2}
f(**kwargs)  # this call is equal to f(a=1, b=3)

There is similar mechanism for positional arguments in Python:
args = [1, 2]
f(*args)  # this call is equal to f(1, 2)

[web2py] Re: dynamic keywords on database update

[Mchurch]

thanks a lot!

On 23 Feb, 15:19, Anthony  wrote:
> On Thursday, February 23, 2012 2:27:44 AM UTC-5, Mchurch wrote:
>
> > **{'%s%s' % (Keyword, n): checked})
> > Anthony, can you explain it better? It's something that I would like
> > to understand very well.
>
> '%s%s' % (Keyword, n) is Python string formatting -- if Keyword is "hello"
> and n is 5, it will produce the string "hello5". Now, suppose "checked" is
> a boolean value equal to True -- then the above will produce the following
> dictionary:
>
> {hello5: True}
>
> In Python, you can pass a dictionary to a function and precede it with **,
> and that is equivalent to passing each item in the dictionary to the
> function as a separate keyword argument. So,
>
> update(**{hello5: True})
>
> is equivalent to
>
> update(hello5=True)
>
> Of course, the "hello5" is generated dynamically, so we can't use the
> latter syntax, but we can construct a dictionary with a dynamically
> generated key, which enables us to use the former syntax.
>
> Anthony

[web2py] Re: dynamic keywords on database update

[Anthony]

On Thursday, February 23, 2012 2:27:44 AM UTC-5, Mchurch wrote:
>
> **{'%s%s' % (Keyword, n): checked}) 
> Anthony, can you explain it better? It's something that I would like 
> to understand very well.
>

'%s%s' % (Keyword, n) is Python string formatting -- if Keyword is "hello" 
and n is 5, it will produce the string "hello5". Now, suppose "checked" is 
a boolean value equal to True -- then the above will produce the following 
dictionary:

{hello5: True}

In Python, you can pass a dictionary to a function and precede it with **, 
and that is equivalent to passing each item in the dictionary to the 
function as a separate keyword argument. So,

update(**{hello5: True})

is equivalent to

update(hello5=True)

Of course, the "hello5" is generated dynamically, so we can't use the 
latter syntax, but we can construct a dictionary with a dynamically 
generated key, which enables us to use the former syntax.

Anthony

[web2py] Re: dynamic keywords on database update

[Mchurch]

**{'%s%s' % (Keyword, n): checked})
Anthony, can you explain it better? It's something that I would like
to understand very well.
Tnx.

On 22 Feb, 20:33, Anthony  wrote:
> > I have a simple question in turn. How is it possible to make keyword
> > search criteria dynamic? For example:
>
> > db(Orders.id==id).update(Keyword+n = checked)
>
> > where n is any number?
>
> db(Orders.id==id).update(**{'%s%s' % (Keyword, n): checked})
>
> Anthony

[web2py] Re: dynamic keywords on database update

[Anthony]

>
> I have a simple question in turn. How is it possible to make keyword 
> search criteria dynamic? For example: 
>
> db(Orders.id==id).update(Keyword+n = checked) 
>
> where n is any number?


db(Orders.id==id).update(**{'%s%s' % (Keyword, n): checked})

Anthony