  The spin effects in the hadronization process have been included for the
first time in the PYTHIA 8 event generator. The spin effects are limited to the
production of pseudo-scalar mesons and are obtained from the propagation of the
quark polarization along the fragmentation chain according to the rules of the
so-called $^3P_0$ model. The interface between PYTHIA 8 and the package of the
$^3P_0$ model is presented together with preliminary results on the Collins and
di-hadron asymmetries as obtained from simulations of the transversely
polarized semi-inclusive deep inelastic scattering process.
