import atexit
class AutoCloseMeta(type):
"Tracks the instances and closes them in reverse instantiation order"
def __new__(mcl, name, bases, dic):
cls = super(AutoCloseMeta, mcl).__new__(mcl, name, bases, dic)
cls.closeall # assert the method closeall exists
cls._open_instances = [] # objects not closed yet
return cls
def __call__(cls, *args, **kw):
# tracks the instances of the instances
self = super(AutoCloseMeta, cls).__call__(*args, **kw)
cls._open_instances.append(self)
return self
def closeall(cls):
"Recursively close all instances of cls and its subclasses"
print 'Closing instances of %s' % cls # you may remove this print
for obj in reversed(cls._open_instances):
obj.close()
cls._open_instances.remove(obj)
for subc in cls.__subclasses__():
subc.closeall()
class AutoClose(object):
"Abstract base class"
__metaclass__ = AutoCloseMeta
atexit.register(AutoClose.closeall)
if __name__ == '__main__': # test
import logging
class C(AutoClose):
def __init__(self, id):
self.id = id
def close(self):
logging.warn('closing object %s' % self.id)
class D(C):
pass
c1 = C(1)
c2 = C(2)
d3 = D(3)
