Aaron Brady <castiro...@gmail.com> wrote: > Th.1 Th.2 > a=X > a=Y > a=Z > > You are saying that if 'a=Z' interrupts 'a=Y' at the wrong time, the > destructor for 'X' or 'Y' might not get called. Correct? In serial > flow, the destructor for X is called, then Y.
No, the destructors will be called, but the destructors can do pretty much anything they want so you can't say the assignment is atomic. This isn't actually a threading issue: you don't need multiple threads to experience werid issues here. If you do strange things in a destructor then you can come up with confusing code even with a single thread. > >> Other nasty things can happen if you use dictionaries from multiple >> threads. You cannot add or remove a dictionary key while iterating over >> a dictionary. This isn't normally a big issue, but as soon as you try to >> share the dictionary between threads you'll have to be careful never to >> iterate through it. > > These aren't documented, IIRC. Did you just discover them by trial > and error? > It is documented, but I can't remember where for Python 2.x. For Python 3, PEP 3106 says: "As in Python 2.x, mutating a dict while iterating over it using an iterator has an undefined effect and will in most cases raise a RuntimeError exception. (This is similar to the guarantees made by the Java Collections Framework.)" -- Duncan Booth http://kupuguy.blogspot.com -- http://mail.python.org/mailman/listinfo/python-list
