Family of snakes (suborder serpentes), that are amongst hobbyists generaly appreciated for their calm and docile nature. The group is closely related to boas and anacondas and together these three groups are known as snakes of the old world.

Contrary to common belief these three groups (pythons, boas and anacondas) do not represent the (evolutionary) oldest groups of snakes, that would be the Typhlopidae or "Blind Snakes"

The whole group is non-venomous, killing its prey by constriction. This type of constriction does not mean that they choke their prey to death by closing of their trachea or windpipe. It means that the snake throws a loop (or a number of loops, depending on the size of the prey, relative to the snake) of its body around the chest of its prey, and slowly tightens this loop. Thus making it impossible for the prey to inhale. This of course results in the death of the prey, after which the loop of the snake which is wound around the prey's body is tightend once more, to break the preys ribs in order to be able to swallow it easier.

The largest snake in the world (in length, not weight) is a Reticulated Python (see this) which can get up to about 10 meters long (which is longer than a dubbeldecker bus!), altough other species (such as the Anthill Python (Antharesia perthensis)) stay very small (adults grow to about 60 cm). The heaviest snake in the world, by the way, is an Anaconda (Eunectes murinus) which can weigh over 250 kilos, and is unable to support its own weight on dry land (This is not a member of the Pythonidea Family thought).