Compose two or more schemas into one - see https://github.com/keleshev/schema/pull/169 for details.

schema_compose.py

from schema import Schema, _priority, DICT, Optional


def compose(*schemas, **kwargs):
    """Compose two or more schemas into one.

    See https://github.com/keleshev/schema/pull/169 for details.
    """
    reduce = kwargs.pop("reduce", lambda schemas: schemas[0])
    if not callable(reduce):
        if callable(getattr(reduce, "validate", None)):
            reduce = reduce.validate
        else:
            msg = "Expected a callabled or validator, not %r"
            raise TypeError(msg % reduce)
    schemas = [s._schema if isinstance(s, Schema) else s for s in schemas]
    priorities = set(map(_priority, schemas))
    if priorities == {DICT}:
        optionals = set()
        to_compose = {}
        for s in schemas:
            for k, v in ((k, s[k]) for k in s):
                if isinstance(k, Optional):
                    if k.key in to_compose:
                        continue
                    else:
                        optionals.add(k.key)
                elif k not in optionals:
                    comp = to_compose.setdefault(k, [])
                    comp.append(v)
        new = {}
        for k, v in to_compose.items():
            if len(v) > 1:
                new[k] = compose(*v, reduce=reduce)
            else:
                new[k] = v[0]
        return Schema(new, **kwargs)
    else:
        return Schema(reduce(schemas), **kwargs)