This paper presents the toolkit SNAKES, focusing on the ability to model Petri nets whose tokens are Petri nets (so called nets in nets). SNAKES is a general Petri net library that allows to model and execute Python-coloured Petri nets: tokens are Python objects and net inscriptions are Python expressions. Since SNAKES itself is programmed in Python, Petri net inscriptions can handle Petri net objects as data values, for instance as tokens.