def ode1():
    """
    First order ode from Learning Scipy for Numerical and Scientific computing
    """
    import numpy
    from scipy.integrate import ode
    f = lambda t, y: -20 * y
    actual_solution = lambda t: numpy.exp(-20 * t)
    dt = 0.1
    solver = ode(f).set_integrator('dop853')
    solver.set_initial_value(1, 0)
    while solver.successful() and solver.t <= 1 + dt:
        print(solver.t, solver.y, actual_solution(solver.t))
        solver.integrate(solver.t + dt)
