Nested Mapping

[Paul Rubin]

Raymond Hettinger <python at rcn.com> writes:
> The c.parent.parent.parent chain finds successive enclosing contexts:

I was asking about finding the child contexts, not the parents.  This is
analogous to how you can find the keys in a dict with dict.keys().

>> One question: what should
>>
>>    c["foo"] = 7
>>    d = c.new_child()
>>    del d["foo"]
>>
>> do?  
>
> By default, it raises a KeyError because 'foo' is not in the current
> context.  But if enable_nonlocal is set to True, it removes 'foo' from
> the parent context, c.

I would not have guessed either of those behaviors.  What happens on

  c["foo"] = 7
  d = c.new_child()
  d["foo"] = 8
  del d["foo"]
  print c["foo"], d["foo"]