TST: dataframe constructor should preserve order with standard Python dicts

[arw2019]

We have a couple of dataframe tests (xref #13304) related to column ordering when constructed from an OrderedDict:

pandas/pandas/tests/frame/test_constructors.py

Lines 1250 to 1288 in e4cf3ab

	def test_constructor_ordered_dict_preserve_order(self):
	# see gh-13304
	expected = DataFrame([[2, 1]], columns=["b", "a"])
	data = OrderedDict()
	data["b"] = [2]
	data["a"] = [1]
	result = DataFrame(data)
	tm.assert_frame_equal(result, expected)
	data = OrderedDict()
	data["b"] = 2
	data["a"] = 1
	result = DataFrame([data])
	tm.assert_frame_equal(result, expected)
	def test_constructor_ordered_dict_conflicting_orders(self):
	# the first dict element sets the ordering for the DataFrame,
	# even if there are conflicting orders from subsequent ones
	row_one = OrderedDict()
	row_one["b"] = 2
	row_one["a"] = 1
	row_two = OrderedDict()
	row_two["a"] = 1
	row_two["b"] = 2
	row_three = {"b": 2, "a": 1}
	expected = DataFrame([[2, 1], [2, 1]], columns=["b", "a"])
	result = DataFrame([row_one, row_two])
	tm.assert_frame_equal(result, expected)
	expected = DataFrame([[2, 1], [2, 1], [2, 1]], columns=["b", "a"])
	result = DataFrame([row_one, row_two, row_three])
	tm.assert_frame_equal(result, expected)

As of PEP 468 standard dictionaries are ordered so these tests should also work with OrderedDict replaced by dict

[itsmegarvi]

would doing dict(orderedDict()) work?

[rhshadrach]

Is the current behavior correct and this just needs tests, or is there a bug when using dict instead of OrderedDict?

[arw2019]

Is the current behavior correct and this just needs tests, or is there a bug when using dict instead of OrderedDict?

I think the current behavior is correct so just need tests. I didn't find open issues in the tracker since the OrderedDict ticket was closed four years ago.

would doing dict(orderedDict()) work?

I was thinking of parametrizing the tests on [dict, OrderedDict]. Something like

@pytest.mark.parametrize("dictionary, (dict, OrderedDict)")
def test_foo(dictionary):
    ...

[itsmegarvi]

wouldnt @parametrized("dictionary, (dict, OrderedDict)") do the same thing

[arw2019]

wouldnt @parametrized("dictionary, (dict, OrderedDict)") do the same thing

However you wanna do it yeah

[chethanreddy123]

I don't know where to start contributing, can anyone guide me on how to contribute