On Thu, Jul 11, 2013 at 12:26 AM, Aaron Meurer <asmeu...@gmail.com> wrote: > On Jul 10, 2013, at 9:17 AM, Amit Saha <amitsaha...@gmail.com> wrote: > >> On Wed, Jul 10, 2013 at 1:24 AM, Aaron Meurer <asmeu...@gmail.com> wrote: >>> Yep, strings often (but won't always!) work as input. See >>> https://github.com/sympy/sympy/wiki/Idioms-and-Antipatterns#strings-as-input. >> >> Thanks. Yeah, I have learned that from one of my earlier posts to the >> forum. In this case it should be fine, I guess. >> In fact, I think I made my original query ambiguous: I was really >> asking about passing the symbol to be solved for as a string, >> *not* the expression. > > Even then, you should avoid string. Many arguments to many SymPy > functions accept strings like this, but it's bad practice to use them.
I agree. > >> >> Is this a better approach: >> >>>>> expr = 'x*2 + 5 + y' >>>>> expr=sympify(expr) >>>>> for symbol in expr.atoms(Symbol): >> ... if str(symbol)=='x': >> ... solve(expr, symbol) >> ... >> [-y/2 - 5/2] >> >> So, I look for the symbol I want to solve for and then invoke solve >> using the symbol itself, this having to avoid passing a string. > > It's better to look at symbol.name. Two symbols can have the same > string representation but be unequal. Indeed, thanks for the pointer to symbol.name > > Aaron Meurer > >> >> -- >> http://echorand.me >> >> -- >> 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. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> > > -- > 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. > For more options, visit https://groups.google.com/groups/opt_out. > > -- http://echorand.me -- 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. For more options, visit https://groups.google.com/groups/opt_out.
