[Answer]-Id like to show column total for one of the columns in my table rendered with django-tables2

You can try like this,

class timekeeper(models.Model):
     begin_time = models.DateTimeField()
     begin_time = models.DateTimeField()
     ^^ duplicate field, it should be end_time ??
     timedelta = models.FloatField()

     def save(self):
         self.timedelta = self.end_time - self.begin_time