exact syntax for compute example

[Alex Glaros]

Can anyone please type exact syntax for computed field "personDisplayName" below?

I want to concatenate first_name, a space if possible, and last_name.

auth.settings.extra_fields['auth_user']= [

    Field('personMiddleName','string', label='Middle name'),

    Field('personDisplayName', compute=lambda r: r[first_name] [last_name])

  ]

(I realize field is redundant there is a reason for it.)

thanks!

Alex Glaros

[黄祥]

hm, i think what you need is represent in the field constructor.

e.g. not tested

Field('personDisplayName', represent = lambda personDisplayName, field: '%s %s' % (field.first_name, field.last_name))

best regards,

stifan

[Alex Glaros]

Hi Stifan,

I have a special situation where represent can't work with the business logic.  Has to be a compute.

Any hints for the "compute" syntax?

thanks,

Alex

[黄祥]

i think in compute you must put the row on it (both first_name and last_name) and not sure it can handle string:

e.g. not tested

Field('personDisplayName', compute=lambda r: r[first_name] r[last_name])

another suggestion why not use default? 

or maybe after_insert callback to update the persondisplayname with the combination first_name and last_name value? 

or maybe use on form validation function, assigned the value of persondisplayname base on first_name and last_name form field?

best regards,

stifan

[Alex Glaros]

which ones of those will only work on new record and which ones will work on existing records?

[Alex Glaros]

can't get any of the syntax to work, any hints from this attempt below? (have simplified and removed concatenation)

  Field('personDisplayName', default=lambda r: r'%(first_name)%s')

[黄祥]

default can work both for new insert and update existing.

ref:

http://web2py.com/books/default/chapter/29/06/the-database-abstraction-layer

form validation function can work both for new insert and update existing.

ref:

http://web2py.com/books/default/chapter/29/07/forms-and-validators

callback can work both for new insert and update existing. 

for after new insert, please use : _after_insert 

and 

for after update existing, please use : _after_update

ref:

http://web2py.com/books/default/chapter/29/06/the-database-abstraction-layer#before-and-after-callbacks

best regards,

stifan

[黄祥]

not tested

Field('personDisplayName', default = lambda personDisplayName, field: '%s %s' % (field.first_name, field.last_name) )

best regards,

stifan

[Alex Glaros]

it's getting better but received

<lambda>() takes exactly 2 arguments (0 given)

[Alex Glaros]

I gave up in the model but was successful in the form.  Something like:

  db.auth_user(fieldID).update_record(personDisplayName='%(first_name)s %(last_name)s' % form.vars   

thanks for helping me get it

Alex

[Niphlod]

doesn't

Field('personDisplayName', compute=lambda r: "%s %s" % (r[first_name], r[last_name]))

work  ?

[黄祥]

no it's not work, the point i want to show in here is at the first time the code was :

Field('personDisplayName', compute=lambda r: r[first_name] [last_name])

lack of r on [last_name]

best regards,

stifan

[Niphlod]

it's still an invalid python syntax.
correction to the above....

Field('personDisplayName', compute=lambda r: "%s %s" % (r['first_name'], r['last_name']))

should work.

>>> record = dict(first_name='john', last_name='foo')
>>> result = lambda r : "%s %s" % (r['first_name'], r['last_name'])
>>> result(record)
'john foo'
>>>

[Alex Glaros]

Thanks guys, it worked.

Field('personDisplayName', compute=lambda r: "%s %s" % (r['first_name'], r['last_name']))

How would you identify the workings of each component, I mean does "%s %s" mean "put two strings together here that are identified after the percent sign?"

Much appreciated!

Alex 

[Ron McOuat]

Yes, a Python feature called string formatting

http://docs.python.org/2/library/stdtypes.html#string-formatting-operations

r['first_name'] and r['last_name'] are processed by their str function because of the %s in "%s %s" the format specifier.
The standalone % is the operator specifying string formatting.
The result of the expression is a string containing the two strings with a space separator.

On Saturday, 16 November 2013 22:41:16 UTC-8, Alex Glaros wrote:

Thanks guys, it worked.

Field('personDisplayName', compute=lambda r: "%s %s" % (r['first_name'], r['last_name']))

How would you identify the workings of each component, I mean does "%s %s" mean "put two strings together here that are identified after the percent sign?"

Much appreciated!

Alex 

[Alex Glaros]

Thanks Ron. I didn't immediately grasp that I should have been learning Python concurrently. Alex