[web2py] DAL update with date arithmetic

[Simon Ashley]

Uncertain why the first fails with the following error:

TypeError: unsupported operand type(s) for -: 'datetime.datetime' and 
'Field'

and the second works.

def Update_RData3_dslr():
    import datetime
    today = datetime.date.today()
    db(db.HData.id>0 and db.HData.lrace).update(dslr = (request.now - db.
HData.lrace).days)

  
                                                                            
        
def Update_RData4_dslr():
    import datetime
    today = datetime.date.today()
    rows = db(db.HData.id>0 and db.HData.lrace).select(db.HData.id, db.HData
.lrace)
    for row in rows:
        dslr = (today - row.lrace).days
        db(db.HData.id == row.id).update(dslr = dslr)

TIA

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