Your __del__ method assumes that the class is still present by the time it is called. This assumption is incorrect. Groupclass has already been cleared when your Python program exits and is now set to None. Test if the global reference to the class still exists first: def __del__(self): if Groupclass: Groupclass.count -= 1 or … Read more
In CPython, at least, files are closed when the file object is deallocated. See the file_dealloc function in Objects/fileobject.c in the CPython source. Dealloc methods are sort-of like __del__ for C types, except without some of the problems inherent to __del__.
The del statement doesn’t reclaim memory. It removes a reference, which decrements the reference count on the value. If the count is zero, the memory can be reclaimed. CPython will reclaim the memory immediately, there’s no need to wait for the garbage collector to run. In fact, the garbage collector is only needed for reclaiming … Read more
No no no. Python has a garbage collector that has very strong territory issues – it won’t mess with you creating objects, you don’t mess with it deleting objects. Simply put, it can’t be done, and for a good reason. If, for instance, your need comes from cases of, say, caching algorithms that keep references, … Read more
You cannot assume that __del__ will ever be called – it is not a place to hope that resources are automagically deallocated. If you want to make sure that a (non-memory) resource is released, you should make a release() or similar method and then call that explicitly (or use it in a context manager as … Read more
The del statement removes an element: del d[key] Note that this mutates the existing dictionary, so the contents of the dictionary changes for anybody else who has a reference to the same instance. To return a new dictionary, make a copy of the dictionary: def removekey(d, key): r = dict(d) del r[key] return r The … Read more
Firstly, you can del other things besides local variables del list_item[4] del dictionary[“alpha”] Both of which should be clearly useful. Secondly, using del on a local variable makes the intent clearer. Compare: del foo to foo = None I know in the case of del foo that the intent is to remove the variable from … Read more