Hi, I'm writing a program that requires extensive use of scipy.integrate.odeint (tracing paths around a black hole). It mostly works well but has certain frustrating features. (1) It is apparently impossible to prevent it from printing to the standard output. This is wrong; if it must output error messages, they should go on standard error, so as not to contaminate the output of my program. It would also be nice to be able to turn them off! Or, more specifically, to signal the error conditions in a way I can reasonably test for. String matching on info["messages"] is not at all satisfactory. (2) It is very difficult to control what happens when an error occurs. When a function called from inside odeint throws an exception (undefined variable, overflow error, what have you), odeint catches it, prints a backtrace (to standard error, at least, thankfully), and continues trying more points. Since what has usually happened is that odeint has run into a singularity, it grinds away endlessly, spewing page after page of the same error message, before finally giving up. An error is then signaled by leaving info["mused"][n]==0. Ideal for my purposes would be for odeint simply not to catch exceptions, or to treat exceptions as an instruction to return early. Failure to integrate over the whole range of t could be signaled by raising an exception. This would allow easy catching of integration failures, and it would also (for example) allow me to signal that the ray had proceeded into a forbidden region by throwing an exception. I realize that nobody is very keen on rooting around inside the FORTRAN code for odeint, and I can't see directly how to make it stop immediately. It should be fine for the user function to simply return NaNs. Another option is, if the integration falls apart at some point, to simply stop and provide information about how far the integration successfully progressed. lsoda.f is definitely capable of this without modification. Thanks. A. M. Archibald