Returns a list of differences between two JSON objects - useful for smarter unit test error messages

json_diffs.py

def json_diffs(a, b, path='_'):
    errors = []
    if type(a) != type(b):
        return ['%s: Type of a (%s) != type of b (%s)' % (path, type(a), type(b))]
    if type(a) == dict:
        for key in a:
            new_path = path + ('[%s]' % key)
            if key not in b:
                errors.append('%s: Key %s present in a but not in b' % (new_path, key))
            else:
                errors.extend(json_diffs(a[key], b[key], new_path))
        for key in b:
            new_path = path + ('[%s]' % key)
            if key not in a:
                errors.append('%s: Key %s present in b but not in a' % (new_path, key))
    elif type(a) == list:
        if len(a) != len(b):
            errors.append('%s: len(a) (%s) != len(b) (%s)' % (path, len(a), len(b)))
        for i, item in enumerate(a):
            errors.extend(json_diffs(item, b[i], path=path + '[%s]' % i))
    else:
        if a != b:
            errors.append('%s: a != b (%r != %r)' % (path, a, b))
    return errors