geoff.ba...@gmail.com writes: > I have a multithreaded application using an embedded Python 3.6.4 (upgraded > from 3.6.2 today in the hope that the problem was now solved: it doesn't seem > to be). The standard library is in a zip file. So long as only one thread is > running Python at a time it seems to work fine. But there seems to be a > problem with the module importing when several Python threads are active. > > I get a variety of errors indeterministically, usually indicating that some > symbol hasn't been imported. This occurs both in my own code and in the > standard library. The most frequent is probably this line:
I do not know your specific problem (up to now, I used only Python 2), but I know about import problems in multi threaded applications. The problem is easily understood: import affects the global object "sys.modules". To protect this object, Python must do something. In former Python versions (somewhere before Python 3), it was using a a thread lock: this could cause a deadlock in the case of some import dependencies. The recoomendation to avoid the problem has been to avoid module level imports for modules imported by threads. Python 3 may have changed the way to protect "sys.modules". In case of recursive import dependencies, you may see that some symbols are not defined even in single threaded applications -- however then usually deterministically. At your place, I would start to check whether your application has recursive import dependancies -- and in this case, remove them. -- https://mail.python.org/mailman/listinfo/python-list
