Schema Analysis for TinyDB

main.py

from schema import Schema
s = Schema.from_iterable([
    {'key': True, 'maybe': 1},
    {'key': None, 'maybe': True},
    {'key': False},
])
print(s)
# => {'key': <Key [bool]>, 'maybe': <Maybe [bool, int]>}

schema.py

def clsname(obj):
    return obj.__name__



class Schema(dict):
    def __init__(self, initial):
        for key, value in initial.items():
            self[key] = Key([type(value)])

    def update(self, v):
        keys = set(v).union(self)

        for key in keys:
            if key not in v:
                self[key] = Maybe.from_key(self[key])
                continue
            if key not in self:
                self[key] = Maybe([])
            self[key].add_obj(v[key])

    @classmethod
    def from_iterable(cls, it):
        it = iter(it)
        self = cls(next(it))
        for item in it:
            self.update(item)
        return self


class Key(object):
    def __init__(self, types):
        self.types = set(types)

    def add_obj(self, obj):
        self.types.add(type(obj))

    def __repr__(self):
        return '<%s [%s]>' % (
                clsname(self.__class__),
                ', '.join([clsname(i) for i in self.types]),
                )


class Maybe(Key):
    @classmethod
    def from_key(cls, key):
        return Maybe(key.types)

That's great, thanks!

Just for reference: tinydb#44: Examine structure of database