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Ensure that DataFrame constructed from dict follows insertion order #25915

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ebb3f8c
Fixed pep8 issues
alexander-ponomaroff Mar 29, 2019
d2ec8ac
Fix indentation mistake
alexander-ponomaroff Mar 29, 2019
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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v0.25.0.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -395,7 +395,7 @@ Sparse
Other
^^^^^

-
- Ensured that ``DataFrame`` constructed from a ``dict`` with no index passed will follow the ``dict``'s insertion order (:issue:`25911`)
-
-

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2 changes: 1 addition & 1 deletion pandas/core/internals/construction.py
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Expand Up @@ -302,7 +302,7 @@ def extract_index(data):
' an index')

if have_series or have_dicts:
index = _union_indexes(indexes)
index = _union_indexes(indexes, sort=False)

if have_raw_arrays:
lengths = list(set(raw_lengths))
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17 changes: 14 additions & 3 deletions pandas/tests/frame/test_constructors.py
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Expand Up @@ -314,6 +314,17 @@ def test_constructor_dict(self):
with pytest.raises(ValueError, match=msg):
DataFrame({'a': 0.7}, columns=['a'])

def test_constructor_dict_order(self):
data = {'B': {'b': 1, 'c': 2, 'a': 3},
'A': {'b': 3, 'c': 2, 'a': 1}}
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What happens if the order isn't the same across all dicts?

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It would keep the order of the first dict. For example if the first dict is ordered b, c, a like in the above example and the second dict is ordered c, b, a - the resulting DataFrame would maintain the order b, c, a.

result = pd.DataFrame(data)

expected = pd.DataFrame([[1, 3], [2, 2], [3, 1]],
index=['b', 'c', 'a'],
columns=['B', 'A'])

tm.assert_frame_equal(result, expected)

@pytest.mark.parametrize("scalar", [2, np.nan, None, 'D'])
def test_constructor_invalid_items_unused(self, scalar):
# No error if invalid (scalar) value is in fact not used:
Expand Down Expand Up @@ -479,7 +490,7 @@ def test_constructor_subclass_dict(self):
dct.update(v.to_dict())
data[k] = dct
frame = DataFrame(data)
tm.assert_frame_equal(self.frame.sort_index(), frame)
tm.assert_frame_equal(self.frame, frame)

def test_constructor_dict_block(self):
expected = np.array([[4., 3., 2., 1.]])
Expand Down Expand Up @@ -1110,7 +1121,7 @@ def test_constructor_list_of_series(self):

sdict = OrderedDict(zip(['x', 'Unnamed 0'], data))
expected = DataFrame.from_dict(sdict, orient='index')
tm.assert_frame_equal(result.sort_index(), expected)
tm.assert_frame_equal(result, expected)

# none named
data = [OrderedDict([['a', 1.5], ['b', 3], ['c', 4], ['d', 6]]),
Expand Down Expand Up @@ -1231,7 +1242,7 @@ def test_constructor_namedtuples(self):
def test_constructor_orient(self):
data_dict = self.mixed_frame.T._series
recons = DataFrame.from_dict(data_dict, orient='index')
expected = self.mixed_frame.sort_index()
expected = self.mixed_frame
tm.assert_frame_equal(recons, expected)

# dict of sequence
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