[web2py] db.field.name.represent question

[Frank]

hi,
In my model,
db.define_table('task',Field('title'),......)
db.task.title.requires=IS_NOT_EMPTY()
I write following,
db.task.title.represent = lambda
t:A(t,_href=URL(r=request,c='default',f='data/edit/task',args=db.task[t].id))

there are erros in args, for args, I try to get link
default/data/edit/task/task.id.I can not figure it out, please advise.
Frank