Runge-Kutta ODE Integrator Implemented in Cython and Numba CyRK provides fast integration tools to solve systems of ODEs using an adaptive time stepping scheme. CyRK can, usually, accept differential equation functions that are written in pure Python, njited numba, or cython-based cdef classes. These kinds of functions are generally easier to implement than pure c functions. Using CyRK can speed up development time while not making a huge sacrifice when it comes to performance. The purpose of this package is to provide some functionality of scipy's solve_ivp with greatly improved performance. Currently, CyRK's numba (njit-safe) implementation is 10-100x faster than scipy's solve_ivp function. The cython cyrk_ode function that works with python (or numba) functions is 5-40x faster than scipy. The cython CySolver class that works with cython-based cdef classes is 5-400x faster than scipy. An additional benefit of the two cython implementations is that they are pre-compiled. This avoids most of the start-up performance hit experienced by just-in-time compilers like numba. To install simply run: `pip install CyRK` from a terminal where python 3.8-3.11 has been installed. If you run into problems please check out the GitHub page for troubleshooting help or get in touch. CyRK is open-source and we encourage you to learn more and contribute to its development. Find out how you can help here.