dictsurvey.py

def collect_keys(d):
    if not isinstance(d, dict):
        return []
    level = d.keys()
    for k, v in d.items():
        level.extend('%s.%s' % (k, c) for c in collect_keys(v))
    return level


def analyze(paths):
    survey = {}
    for p in paths:
        survey[p] = survey.setdefault(p, 0) + 1

    return survey


def survey_dicts(lod):
    return analyze([path
                    for d in lod
                    for path in collect_keys(d)])


lod = [{'d': {'c': 1, 'e': 2}, 'a': 3},
       {'d': {'c': 1, 'f': 1}},
       {'a': 4}]

print survey_dicts(lod)