Some row questions

[Dave S]

I have a fairly straight forward table, and a fairly easy db query:

db(db.segment.parent == request.vars.id).select()

For my use case, this returns a Rows object of 3 to 10 Row objects, and I do some simple calculations.

for row in rows:
  if row.x:
     term1 = row.term
  if row.y:
     term2  = row.term
return dict(rows=rows, mycalc = calc(term1,term2))

(ok, x is really "isstart" and y is "isstop", flags to mark endpoints, but that's being overly specific)

I'd also like to compute a delta between the row.term value of each row and it's predecessor (by data entry convention, the table is ordered by id).  So the 2 questions are:

• can you tell the index in rows of the row you are working on?  (I guess this is a Python question, not just web2py).  In js, the map and reduce functions know the index in the array they have as input; is something similar available in a Python iteration?
• can you add fields to a Row object, or to the parent Rows object, and have the view display it, or is a virtual field definition needed?

Thanks.

Dave S

/dps

[villas]

Hi Dave,

Open your app on the commandline:

python web2py.py -S yourapp -M

Experiment a little...

1.  for i, row in enumerate(rows)
2.  rows[0].test = 'whatever'

[Dave S]

On Friday, June 23, 2017 at 1:24:30 PM UTC-7, villas wrote:

Hi Dave,

Open your app on the commandline:

python web2py.py -S yourapp -M

Experiment a little...

1.  for i, row in enumerate(rows)
2.  rows[0].test = 'whatever'

I've kinda already done that.  No tee-shirt appeared.

/dps
 

[villas]

I've kinda already done that.  No tee-shirt appeared.

I guess we don't always get what we'd like.  :)

So why doesn't enumerate() provide an index?  Or, maybe that's not the kind of index you wanted?

If you add something to the rows object, why isn't it available in the view?

Try this:

def test():
    rows = db(db.yourtable.id < 20).select(db.yourtable.id) 
    for i, r in enumerate(rows):   
        rows[i].test = 'my_extra_value_%s' % i
    tbl = TABLE([ TR(j.id, j.test) for j in rows ])
    return dict(tbl=tbl)