On Sun, 16 Nov 2014 08:14:05 +0100, dieter wrote: > "Charles T. Smith" <cts.private.ya...@gmail.com> writes: >> Now, I'm getting these errors: >> >> ImportError: cannot import name ... >> >> and >> >> AttributeError: 'module' object has no attribute ... >> >> (what is 'module'?) >> >> Is there a way to resolve this without having to restructure my code >> every couple of days? >> >> I thought using imports of the form: >> >> from module import symbol >> >> was the "right way" to avoid these hassles... > > I have not noticed your previous posts regarding import problems -- > thus, I may repeats things already said. > > Usually, Python imports are straight forward and do not lead to > surprises. There are two exceptions: recursive imports and imports in > separate threads. Let's look at the problem areas in turn. > > Recursive imports. In this case you have module "A" which imports module > "B" (maybe indirectly via a sequence of intervening imports) which > imports module "A". In this, "import" means either "import ..." or "from > ... import ..." (it does not matter). When module "B" tries to import > module "A", then "A" is not yet complete (as during the execution of > "A"'s initialization code, it started to import "B" (maybe indirectly) > and the following initialization code has not yet been executed). As a > consequence, you may get "AttributeError" (or "ImportError") when you > try to access things from "A". To avoid problems like this, try to avoid > recursive imports. One way to do this, are local imports -- i.e. imports > inside a function. This way, the import happens when the functions is > called which (hopefully) happens after module initialization.
Yes, we're talking about recursive imports here. It's a complex, object- oriented system with big classes and little classes that are strongly interrelated. I can get the imports configured properly so everything works but if I make a little change to the code, then suddenly all my imports are broken and I must painstakingly go through the whole structure, reorganizing them. Are others equally frustrated by this or is there a trick or principle that I'm missing. At this point, I guess the way I'll have to proceed is to put every class in its own file, no matter how small. Hopefully that takes care of the problem. I compared perl's object-oriented philosophy with python's and didn't like how perl *requires* you to put everything into its own file. Now it looks like python does, too, implicitly. cts www.creative-telcom-solutions.de -- https://mail.python.org/mailman/listinfo/python-list
