[Scipy-tickets] [SciPy] #1187: ode crashes if rhs returns a tuple instead of a list

SciPy Trac scipy-tickets@scipy....
Sat Jan 5 06:26:43 CST 2013

#1187: ode crashes if rhs returns a tuple instead of a list
 Reporter:  miha                                        |       Owner:  somebody   
     Type:  defect                                      |      Status:  new        
 Priority:  normal                                      |   Milestone:  Unscheduled
Component:  scipy.integrate                             |     Version:  0.7.0      
 Keywords:  integrade, ode, PyObject_Call, tuple, list  |  

Comment(by rgommers):

 The first line of your {{{lorenz_compute}}} function is incorrect.  This
 works as expected:
 import numpy as np
 from scipy import integrate

 # Given state [x, y, z] compute right hand side of the Lorenz equations.
 # The default coefficients compute the canonical attractor.
 def lorenz(t, xyz, coefficients = [10., 8./3., 28.]):
     x, y, z = xyz
     sigma, beta, rho = coefficients
     return [sigma*(y-x), x*(rho-z)-y, x*y-beta*z]

 def lorenz_compute(tf = 1000, dt = 0.1, xyz0 = np.random.randn(3)):
     solver = integrate.ode(lorenz)
     solver.set_initial_value(xyz0, 0)
     soln = []
     while solver.successful() and solver.t < tf:
         solver.integrate(solver.t + dt)
         soln.append([solver.t, solver.y[0], solver.y[1], solver.y[2]])

     return np.array(soln)

 if __name__ == "__main__":
     a = lorenz_compute()

 And then, changing the return of {{{lorenz}}} from list of 3 elements to
 tuple of elements gives the {{{SystemError}}} again.

Ticket URL: <http://projects.scipy.org/scipy/ticket/1187#comment:8>
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