I think it looks good. You can probably can probably do better by creating a generator comprehension rather than creating and indexing into a list (and it's also more pythonic). crawl() is a pretty common pattern. I'm sure you could find an existing version in the SymPy code already.
Also, at line 54, you don't need to assign to val. Just return sub_dict[expr]. At line 56, I think what you really want is "if not expr.args". There are more types of expressions without args than just Symbol and Number. The important thing is to avoid walking the expression tree multiple times. Ideally, you would walk it only once. I think you are here. Aaron Meurer On Wed, Jul 2, 2014 at 9:10 PM, James Crist <crist...@umn.edu> wrote: > I wrote this up today. In physics.mechanics we often have to sub symbols for > values (or a smaller subset of symbols, i.e. the "operating point"). For the > huge expressions generated, `subs` is extremely slow. Also, it subs inside > derivatives, which is not ideal (we are currently using a hacky > work-around). It also seems to be overkill for what's needed. More details > are in the docstring of the attached gist. > > https://gist.github.com/jcrist/8ce1a79dfe0b42723550 > > I'd like some serious code design review of this. Is what I'm doing (direct > naive replacement) bad? Is there a better way, that doesn't sacrifice speed? > Note that for expressions of this size, xreplace, replace, and subs all > perform equally poorly. > > > -- > You received this message because you are subscribed to the Google Groups > "PyDy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to pydy+unsubscr...@googlegroups.com. > To post to this group, send email to p...@googlegroups.com. > Visit this group at http://groups.google.com/group/pydy. > 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%3D6JZeTUqVX6avcB1jVEvxtidrtKgpZaiFzvxgfxQOdPkQA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
