When exoplanets pass in front of their stars, they imprint a transit signature on the stellar light curve which to date has been assumed to be symmetric in time, owing to the planet being modelled as a circular area occulting the stellar surface. However, this signature might be asymmetric due to different temperature/pressure and/or chemical compositions in the different terminator regions of the transiting planet. catwoman is a Python package that allows to model these asymmetric transit lightcurves, calculating light curves for any radially symmetric stellar limb darkening law, and where planets are modelled as two semi-circles, of different radii, using the integration algorithm developed in Kreidberg (2015) and implemented in the batman library, from which catwoman builds upon.