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BUG: Create empty dataframe with string dtype fails #33651

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Merged
merged 10 commits into from
May 9, 2020
Merged

BUG: Create empty dataframe with string dtype fails #33651

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82dc446
BUG: Create empty dataframe with string dtype fails
kotamatsuoka Apr 19, 2020
d1da8c8
Changes according to comments
kotamatsuoka Apr 20, 2020
66eda6a
Add test of empty dataframe in ExtensionDtype
kotamatsuoka Apr 25, 2020
ff26d95
Remove column fixtures
kotamatsuoka Apr 26, 2020
92d75b7
Remove xfail in test_integer
kotamatsuoka Apr 29, 2020
0363ef0
Merge remote-tracking branch 'upstream/master' into empty-dataframe-w…
simonjayhawkins May 3, 2020
5fcfed6
revert changes to IntegerArray, fix IntervalArray, update test per co…
simonjayhawkins May 3, 2020
5ad5f8b
add a whatsnew.
kotamatsuoka May 5, 2020
9e15301
update the whatsnew
kotamatsuoka May 5, 2020
e8e1ed1
Merge branch 'master' into empty-dataframe-with-string-dtype
kotamatsuoka May 5, 2020
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5 changes: 4 additions & 1 deletion pandas/core/internals/construction.py
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Original file line number Diff line number Diff line change
Expand Up @@ -242,7 +242,10 @@ def init_dict(data, index, columns, dtype=None):

# no obvious "empty" int column
if missing.any() and not is_integer_dtype(dtype):
if dtype is None or np.issubdtype(dtype, np.flexible):
if is_dtype_equal(dtype, "string"):
# GH 33623
nan_dtype = dtype
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this will be dtype.na_value

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can you update this

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Sorry, I can't figure out how to fix this from "this will be dtype.na_value".

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In [15]: pd.Int32Dtype.na_value                                                                                                                                                                                                                          
Out[15]: <NA>

nan_dtype = dtype.na_value

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@kotamatsuoka kotamatsuoka Apr 26, 2020 •
edited
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will change to nan_dtype = dtype.na_value, error occurs.

            if not isinstance(dtype, (np.dtype, type(np.dtype))):
>               dtype = dtype.dtype
E               AttributeError: 'NAType' object has no attribute 'dtype'

pandas/core/dtypes/cast.py:1545: AttributeError

So I updated it like this.

if (
            dtype is None
            or is_extension_array_dtype(dtype)
            or np.issubdtype(dtype, np.flexible)
        ):
    nan_dtype = object

elif dtype is None or np.issubdtype(dtype, np.flexible):
# GH#1783
nan_dtype = object
else:
Expand Down
4 changes: 4 additions & 0 deletions pandas/tests/frame/test_constructors.py
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Expand Up @@ -2679,3 +2679,7 @@ def test_construction_from_set_raises(self):
msg = "Set type is unordered"
with pytest.raises(TypeError, match=msg):
pd.DataFrame({"a": {1, 2, 3}})

def test_construct_empty_dataframe_with_string_dtype(self):
# GH 33623
pd.DataFrame(columns=["a"], dtype="string")