Why is python collecting even if gc disabled?

garbage-collection, python

Solution

Because garbage collection only deals with circular references. Quoting from the `gc` module documention:

Since the collector supplements the reference counting already used in Python, you can disable the collector if you are sure your program does not create reference cycles.

CPython uses reference counting to clean up most objects. When you replace the list `a` referred to with an empty list, the reference counts for the old list dropped to 0, so it is deleted at that point. Deleting the list causes the reference counts for the `Foo()` instances to drop to 0 too, etc.

If you create circular references instead, and disable garbage collection, you'll see the numbers remain constant:

class Foo(object):
    def __init__(self):
         self.bar = Bar(self)

class Bar(object):
    def __init__(self, foo):
        self.foo = foo

Problem

This code ``` import gc gc.disable() print gc.isenabled() print len(gc.get_objects()) class Foo(): pass print len(gc.get_objects()) a=[] print len(gc.get_objects()) for i in xrange(10000): a.append(Foo()) print len(gc.get_objects()) a=[] # Should not collect print len(gc.get_objects()) gc.collect() print len(gc.get_objects()) ``` Produces this output ``` False 3754 3755 3756 13756 3756 3374 ``` I would expect the second to last number to be 13756, because the gc is disabled and when the original `a` list goes out of scope, it should not drop those objects. Apparently python is collecting those objects anyway. Why ? python is 2.7.2

Original source