DAL Select(fields) puzzle

[Rob Paire]

Hi Web2py 

I hope someone can explains this puzzling behavior. The code below was taken from the book, and it works as given, but when I remove the  "yes_or_no" condition from the field list parameters it causes a KeyError('id') error, and I don't understand why. 

    condition = db.person.name.startswith('B')

    yes_or_no = condition.case('Yes', 'No')

    rows = db(db.person.name == 'Bob').select(db.person.name,yes_or_no ).as_dict()  

    rows = db(db.person.name == 'Bob').select(db.person.ALL).as_dict()  

    ## the two select examples above works as expected

    rows = db(db.person.name == 'Bob').select(db.person.name).as_dict()  

This last example in red throws a KeyError('id') error when trying to name specific fields, but  works fine when returning ALL fields, or when a condition is specified.

Thank you

-Rob

[Dave S]

I don't have a complete answer, but it's the as_dict() that throws the error, because it's looking for a key that isn't there.  If you do 

for row in rows:

      print row

 you see that row doesn't have "id" as a key; it only has 'name' as a key.  as_dict() and as_list() must have a requirement for an id field, and if you make your select

rows = db(db.person.name == 'Bob').select(db.person.name,db.person,id).as_dict()

it should work as expected.

[The requirement isn't mentioned in the book]

/dps

[Rob Paire]

Ah! Now it makes sense - Thank you for your help. Exactly the kind of understanding I was looking for.

-Rob