Deep Equality Test for Nested Python Structures

deep_eq.py

# Copyright (c) 2010-2013 Samuel Sutch [[email protected]]
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import datetime, time, functools, operator, types, six

default_fudge = datetime.timedelta(seconds=0, microseconds=0, days=0)


def deep_eq(_v1, _v2, datetime_fudge=default_fudge, _assert=False):
    """
    Tests for deep equality between two python data structures recursing
    into sub-structures if necessary. Works with all python types including
    iterators and generators. This function was dreampt up to test API responses
    but could be used for anything. Be careful. With deeply nested structures
    you may blow the stack.

    Options:
              datetime_fudge => this is a datetime.timedelta object which, when
                                comparing dates, will accept values that differ
                                by the number of seconds specified
              _assert        => passing yes for this will raise an assertion error
                                when values do not match, instead of returning
                                false (very useful in combination with pdb)

    Doctests included:

    >>> x1, y1 = ({'a': 'b'}, {'a': 'b'})
    >>> deep_eq(x1, y1)
    True
    >>> x2, y2 = ({'a': 'b'}, {'b': 'a'})
    >>> deep_eq(x2, y2)
    False
    >>> x3, y3 = ({'a': {'b': 'c'}}, {'a': {'b': 'c'}})
    >>> deep_eq(x3, y3)
    True
    >>> x4, y4 = ({'c': 't', 'a': {'b': 'c'}}, {'a': {'b': 'n'}, 'c': 't'})
    >>> deep_eq(x4, y4)
    False
    >>> x5, y5 = ({'a': [1,2,3]}, {'a': [1,2,3]})
    >>> deep_eq(x5, y5)
    True
    >>> x6, y6 = ({'a': [1,'b',8]}, {'a': [2,'b',8]})
    >>> deep_eq(x6, y6)
    False
    >>> x7, y7 = ('a', 'a')
    >>> deep_eq(x7, y7)
    True
    >>> x8, y8 = (['p','n',['asdf']], ['p','n',['asdf']])
    >>> deep_eq(x8, y8)
    True
    >>> x9, y9 = (['p','n',['asdf',['omg']]], ['p', 'n', ['asdf',['nowai']]])
    >>> deep_eq(x9, y9)
    False
    >>> x10, y10 = (1, 2)
    >>> deep_eq(x10, y10)
    False
    >>> deep_eq((str(p) for p in range(10)), (str(p) for p in range(10)))
    True
    >>> str(deep_eq(range(4), range(4)))
    'True'
    >>> deep_eq(range(100), range(100))
    True
    >>> deep_eq(range(2), range(5))
    False
    >>> import datetime
    >>> from datetime import datetime as dt
    >>> d1, d2 = (dt.now(), dt.now() + datetime.timedelta(seconds=4))
    >>> deep_eq(d1, d2)
    False
    >>> deep_eq(d1, d2, datetime_fudge=datetime.timedelta(seconds=5))
    True
    """
    _deep_eq = functools.partial(deep_eq, datetime_fudge=datetime_fudge,
                                 _assert=_assert)

    def _check_assert(R, a, b, reason=''):
        if _assert and not R:
            assert 0, "an assertion has failed in deep_eq (%s) %s != %s" % (
                reason, str(a), str(b))
        return R

    def _deep_dict_eq(d1, d2):
        k1, k2 = (sorted(d1.keys()), sorted(d2.keys()))
        if k1 != k2:  # keys should be exactly equal
            return _check_assert(False, k1, k2, "keys")

        return _check_assert(operator.eq(sum(_deep_eq(d1[k], d2[k])
                                             for k in k1),
                                         len(k1)), d1, d2, "dictionaries")

    def _deep_iter_eq(l1, l2):
        if len(l1) != len(l2):
            return _check_assert(False, l1, l2, "lengths")
        return _check_assert(operator.eq(sum(_deep_eq(v1, v2)
                                             for v1, v2 in zip(l1, l2)),
                                         len(l1)), l1, l2, "iterables")

    def op(a, b):
        _op = operator.eq
        if type(a) == datetime.datetime and type(b) == datetime.datetime:
            s = datetime_fudge.seconds
            t1, t2 = (time.mktime(a.timetuple()), time.mktime(b.timetuple()))
            l = t1 - t2
            l = -l if l > 0 else l
            return _check_assert((-s if s > 0 else s) <= l, a, b, "dates")
        return _check_assert(_op(a, b), a, b, "values")

    c1, c2 = (_v1, _v2)

    # guard against strings because they are iterable and their
    # elements yield iterables infinitely.
    # I N C E P T I O N
    if isinstance(_v1, six.string_types):
        pass
    else:
        if isinstance(_v1, dict):
            op = _deep_dict_eq
        else:
            try:
                c1, c2 = (list(iter(_v1)), list(iter(_v2)))
            except TypeError:
                c1, c2 = _v1, _v2
            else:
                op = _deep_iter_eq

    return op(c1, c2)


if __name__ == "__main__":
    x1, y1 = ({'a': 'b'}, {'a': 'b'})
    assert deep_eq(x1, y1)

    x2, y2 = ({'a': 'b'}, {'b': 'a'})
    assert not deep_eq(x2, y2)

    x3, y3 = ({'a': {'b': 'c'}}, {'a': {'b': 'c'}})
    assert deep_eq(x3, y3)
    x4, y4 = ({'c': 't', 'a': {'b': 'c'}}, {'a': {'b': 'n'}, 'c': 't'})
    assert not deep_eq(x4, y4)

    x5, y5 = ({'a': [1, 2, 3]}, {'a': [1, 2, 3]})
    assert deep_eq(x5, y5)
    x6, y6 = ({'a': [1, 'b', 8]}, {'a': [2, 'b', 8]})
    assert not deep_eq(x6, y6)

    x7, y7 = ('a', 'a')
    assert deep_eq(x7, y7)
    x8, y8 = (['p', 'n', ['asdf']], ['p', 'n', ['asdf']])
    assert deep_eq(x8, y8)
    x9, y9 = (['p', 'n', ['asdf', ['omg']]], ['p', 'n', ['asdf', ['nowai']]])
    assert not deep_eq(x9, y9)

    x10, y10 = (1, 2)
    assert not deep_eq(x10, y10)

    assert deep_eq((str(p) for p in range(10)), (str(p) for p in range(10)))
    str(deep_eq(range(4), range(4)))

    assert deep_eq(range(100), range(100))
    assert not deep_eq(range(2), range(5))

    import datetime
    from datetime import datetime as dt

    d1, d2 = (dt.now(), dt.now() + datetime.timedelta(seconds=4))
    assert not deep_eq(d1, d2)

    assert deep_eq(d1, d2, datetime_fudge=datetime.timedelta(seconds=5))

    from collections import OrderedDict
    x11, y11 = ({'a': 'b', 'c': 'd'}, OrderedDict({'c': 'd', 'a': 'b'}))
    assert deep_eq(x11, y11)

    x12, y12 = ({'a': 'b', 'c': [{'a':1, 'b':2}]},
                OrderedDict({'c': [{'b':2, 'a':1}], 'a': 'b'}))
    assert deep_eq(x12, y12)