Ian Kelly <ian.g.ke...@gmail.com> Wrote in message: > On Mon, Nov 17, 2014 at 6:20 PM, Dave Angel <da...@davea.name> wrote: >> Ian Kelly <ian.g.ke...@gmail.com> Wrote in message: >>> On Mon, Nov 17, 2014 at 3:17 PM, Dave Angel <da...@davea.name> wrote: >> >>>> In a module that might get tangled in a cycle, avoid global code >>>> that depends on other modules. Instead of putting such >>>> initialization at top level, put inside a function that gets >>>> called after all suspect imports are completed. (That function >>>> has global keywords ). >>> >>> If the problem is that one of those modules would import the current >>> module, then "after all suspect imports are completed" basically means >>> after the current module has finished importing. So what would be >>> responsible for calling such a function? >>> >> >> If one builds a set of modules that cannot avoid recursive >> imports, then one can ask the code that imports it to make a call >> after importing. Or all that is needed to avoid exposing the mess >> is that the top level not be part of the loops. > > This would make the module less reusable though, since the first other > module to import it in one program might still be used in another > program but not be the first other module to import it. Or I suppose > for simplicity it could be required that all importers call the > initialization function, and have the function return immediately if > it's been called previously. However, I don't think there's any way to > do this without ending up with smelly code. >
The smelly code happened when the designer "can't" break the cycle. I understood the question to be "then what." Two-stage initialization is sometimes "needed" in any language and I was just showing it's possible in Python. I once worked on (and then fixed) a build system that could not complete a build from clean. It needed some pieces from a previous build in order to get to the point where it was ready to build those pieces. Recursive depencies at compile and link time. -- DaveA -- https://mail.python.org/mailman/listinfo/python-list