Interesting idea, and a great exercise for learning more about parsing, CSS selectors, and command-line interfaces.<p>One point of (hopefully) constructive criticism: I&#x27;m not completely sold on the CSS selector syntax.  Attribute selectors are semantically meaningful in the DOM, not as much so in Python.<p>Providing a more Pythonic query language might make it easier for users to guess the purpose of queries and to build complex queries of their own.  For instance:<p><pre><code>    class * extends IntegerField
    class FloatField
    class FloatField: def *
    class FloatField: def to*
    from collections import Counter
</code></pre>
or perhaps:<p><pre><code>    class FloatField: def to*(foo)
    for * in *: if * is None
</code></pre>
(or perhaps even `for $1 in <i>: if $1 is None`.  There are probably better ways than what I described to express the wildcard part, especially if you want to distinguish these from `</i>args`, `<i></i>kwargs`...)<p>Anyways, it&#x27;s always awesome to see people putting their work out there, and I hope you&#x27;ll continue to do so!