Python memory release principles

def getInit(class_name):
    """动态加载模块"""
    resultmodule = __import__(class_name, globals(), locals(), [class_name])
    resultclass = getattr(resultmodule, class_name)
    return resultclass()
import threading, time
        
class b:
    def __init__(self, *args, **kwargs):        
        self.name = "b"
        self.class_name = "a"
        print "%s is inited" % (self.name)
        
    def __del__(self):
        print "%s is deleted" % (self.name)
    
    def other_run(self, obj=None):
        if obj:
            obj.run()
    
    def run(self, *args, **kwargs):
        obj = getInit(self.class_name)
        obj.run()
        self.other_run(obj)        
        print "%s is run" % (self.name)
        
def treading():
    n = 0
    c = b()
    while n<2:
        n += 1
        print "\n"
        print "start"
        c.run()
        print "end"
        print "\n"
    
if __name__ == &#39;__main__&#39;:
    param = {}
    th = threading.Thread(target = treading, args = ())
    th.start()
    
exit()

b is inited
start
a is inited
a is run
a is run
b is run
a is deleted
end
start
a is inited
a is run
a is run
b is run
a is deleted
end
b is deleted

def getInit(class_name):
    resultmodule = __import__(class_name, globals(), locals(), [class_name])
    resultclass = getattr(resultmodule, class_name)
    return resultclass()
import threading, time
import a
        
class b:
    def __init__(self, *args, **kwargs):        
        self.name = "b"
        self.class_name = "a"
        self.obj = getInit(self.class_name)
        print "%s is inited" % (self.name)
        
    def __del__(self):
        print "%s is deleted" % (self.name)
    
    def other_run(self):
        if self.obj:
            self.obj.run()
    
    def run(self, *args, **kwargs):
        self.obj.run()
        self.other_run()        
        print "%s is run" % (self.name)
        
def treading():
    n = 0
    c = b()
    while n<2:
        n += 1
        print "\n"
        print "start"
        c.run()
        print "end"
        print "\n"
    
if __name__ == &#39;__main__&#39;:
    param = {}
    th = threading.Thread(target = treading, args = ())
    th.start()
    
exit()

a is inited
b is inited
start
a is run
a is run
b is run
end
start
a is run
a is run
b is run
end
b is deleted
a is deleted