I guess you'll need to subclass whatever printer you are using (StrPrinter or LambdaPrinter probably) and override _print_Add to get this behavior. See http://docs.sympy.org/latest/modules/printing.html.
By the way, what you are doing might be simplified by using lambdify(). And I think the LambdaPrinter should perform the translation you suggest automatically, if you want to submit a patch. Aaron Meurer On Mon, Jun 9, 2014 at 10:09 AM, Anton Akhmerov <anton.akhme...@gmail.com> wrote: > Hi everyone, > > I'm using sympy to automatically apply a certain transformation to symbolic > input and to generate a reasonably efficient numerical function as an output > (I'm creating a finite difference Hamiltonian from a continuum one). My > current plan is to define a bunch of strings containing function definitions > that I'd feed to exec(). The problem that I have currently is with numerical > prefactors and imaginary unit. Sympy functions that generate string form of > expressions like to keep it as 'I', thus turning e.g. "(0.5 + .5j)" into > "(0.5 + 0.5 * I)". I could replace every I with 1j in the output, or modify > the value assigned to I, but this is not really robust, and not efficient, > since at least there's an extra multiplication. So here's my question: how > to generate a string form of an expression where all the numerical > coefficients would be evaluated into float/complex numbers? > > I have found a somewhat suboptimal solution similar to the one described > over here: http://www.mail-archive.com/sympy@googlegroups.com/msg05139.html > . The reason why it is suboptimal is because terms like 0.5 * I will > transform into 0.5 * 1.j instead of 0.5j (and thus an extra unnecessary > multiplication is performed). > > Thanks, > Anton Akhmerov > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > Visit this group at http://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/8586a91c-e70a-43e3-ba70-6a918a6589e7%40googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6KQ_YEUsOZpwgVbqsxbtc1iSQU2gqwY8-SsifQ%2BZSpkCA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
