无法在python中处理整个数据集

def saveobject(obj):

save=(obj.field1, obj.field2, obj.field3)

con = sqlite3.connect('test.db')

with con:
    cur = con.cursor() 
    cur.execute("CREATE TABLE IF NOT EXISTS Users(field1 TEXT, field2 INT, field3 INT)")   
    allrows = cur.fetchall()
    print allrows
    if(len(allrows)==0):
        cur.execute("INSERT INTO Users VALUES(?,?,?)", save)
    else:
        for row in allrows: 
            if(obj.field1==row[0]):
                if(obj.field2==row[1]):
                    print 'Object already Present'
                    break
                else:
                    print 'Object field2 updated'
                    cur.execute("UPDATE Users set field2=(?) where field1=(?)", (obj.field2, obj.field1))
                   break
            else:
                cur.execute("INSERT INTO Users VALUES(?,?,?)", save)   
                print 'User added'

    print 'after ', cur.fetchall()