Python WeakValueDict text

gistfile1.py

from weakref import WeakValueDictionary

class A(object): pass

# We want to make sure that the weak value dict loses keys
# that are not referenced anymore

d = WeakValueDictionary()
a = A() ; b = A()
d[id(a)] = a
d[id(b)] = b

# We have two items at first
print d.items()
assert len(d) == 2
del a

# then only one, after deleting the reference to a
print d.items()
assert len(d) == 1
del b

# then none, after deleting the reference to b
print d.items()
assert len(d) == 0

# And now, will it work if we don't del?
def f():
	a = A() ; b = A()
	d[id(a)] = a
	d[id(b)] = b
	assert len(d) == 2
f()
print d.items()
assert len(d) == 0

# EOF