tools.py

import colander


def none_to_null(d):
    r = dict()
    for key in d:
        val = d[key]
        if val is None:
            val = colander.null
        r[key] = val
    return r


def null_to_none(d):
    r = dict()
    for key in d:
        val = d[key]
        if val is colander.null:
            val = None
        r[key] = val
    return r