Is there a clever way to pass the key to defaultdict's default_factory?
<p>A class has a constructor which takes one parameter:  </p>

<pre><code>class C(object):
    def __init__(self, v):
        self.v = v
        ...
</code></pre>

<p>Somewhere in the code, it is useful for values in a dict to know their keys.<br>
I want to use a defaultdict with the key passed to newborn default values:  </p>

<pre><code>d = defaultdict(lambda : C(here_i_wish_the_key_to_be))
</code></pre>

<p>Any suggestions?</p>
