[web2py] Number of records

[Rick]

Hi,
In addition to the records that are submitted with a SQLFORM, I want
to give each record a specific "identification" number, so that the
first record has number=1 and so on:

==from model/db.py==
db.define_table('input',
        Field('number', 'integer'),
        Field('value', 'integer'))

...My problem is that I don't know how to automatically add the number
to this form:
form = SQLFORM(db.input, fields=['value'])

Thanks in advance for help.