In some species of snakes it is common. In many reptiles it is standard.
It is rare (but, not impossible) for a ball python to have parthenogenesis and lay viable eggs without mating.
It is more common (but, still uncommon) for a ball python female to have an internal hormone imbalance that results in slug eggs being produced.
If you would like to have viable eggs: I recommend getting your ball python sexed and buying a potential mate.