Yeah, it looks good. I've totally been needing this for some work I'm doing too. The fact that mechanics expressions are a small subset of sympy expressions is a good reason to optimize stuff like this.
In the docstring 3.) trig_funcs aren't the only type of functions. I think you will need to assume that any function (standard sympy ones or custom funcs) can be present in expressions. Just something to keep in mind. Jason moorepants.info +01 530-601-9791 On Wed, Jul 2, 2014 at 11:55 PM, Aaron Meurer <asmeu...@gmail.com> wrote: > 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 > "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/CAP7f1Ait5eoK7EjxQSGDtBECEeguzUTht64yA8jtFTRBZ0gT%2Bw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
