On Mon, Apr 30, 2012 at 9:54 AM, Aaron Meurer <asmeu...@gmail.com> wrote: > Hi. > > Here's what I want to do. I have the semidiscrete free Schrödinger > equation, I*psi(n, t).diff(t) + (psi(n + 1, t) + psi(n - 1, t) - > 2*psi(n, t))/h**2 == 0. I want to substitute the particular solution > psi(n, t) = z**n*exp(-I*omega(z)*t). I can't just use subs, because, > for example, eq.subs(psi(n, t), z**n*exp(-I*omega(z)*t)) will only > replace psi(n, t), but not psi(n + 1, t) or psi(n - 1, t). If I had > first typed def psi(n, t): return z**n*exp(-I*omega(z)*t) and just > entered the Schrödinger equation, it would work.
This is replace type 1.2 (as described in replace's docstring): >>> psi=Function('psi') # you have to make this a function (cf issue 1612) >>> eq= I*psi(n, t).diff(t) + (psi(n + 1, t) + psi(n - 1, t) - ... 2*psi(n, t))/h**2 >>> print filldedent(str(eq.replace(psi, lambda n, t: >>> z**n*exp(-I*omega(z)*t)))) I*Derivative(z**n*exp(-I*t*omega(z)), t) + (-2*z**n*exp(-I*t*omega(z)) + z**(n - 1)*exp(-I*t*omega(z)) + z**(n + 1)*exp(-I*t*omega(z)))/h**2 /c -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.