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Implement PeriodIndex.difference without object-dtype cast #30697

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Merged
merged 4 commits into from
Jan 5, 2020
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Implement PeriodIndex.difference without object-dtype cast #30697

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c1c235f
Implement PeriodIndex.difference without object-dtype cast
jbrockmendel Jan 4, 2020
c7c4179
Merge branch 'master' of https://github.com/pandas-dev/pandas into re…
jbrockmendel Jan 4, 2020
df31072
Merge branch 'master' of https://github.com/pandas-dev/pandas into re…
jbrockmendel Jan 4, 2020
b7dd412
use take_1d with unique._values
jbrockmendel Jan 4, 2020
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5 changes: 4 additions & 1 deletion pandas/_testing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -619,7 +619,10 @@ def _get_ilevel_values(index, level):
# accept level number only
unique = index.levels[level]
level_codes = index.codes[level]
filled = take_1d(unique.values, level_codes, fill_value=unique._na_value)
if is_extension_array_dtype(unique):
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this is not as nice (though its only for testing), won't unique.take(...) work here?

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ill give it a shot

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Turns out this unique.take(...) wont work here. the trouble is that we are calling _shallow_copy below (presumably for perf) and using unique.take ends up passing the wrong types to shallow_copy

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using unique.take ends up passing the wrong types to shallow_copy

then i'd rather not change this, take_1d just does the right thing, so why change it?

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Looks like passing unique._values instead of unique.values fixes the problem cleanly

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ok great

filled = unique.take(level_codes, fill_value=unique._na_value)
else:
filled = take_1d(unique.values, level_codes, fill_value=unique._na_value)
values = unique._shallow_copy(filled, name=index.names[level])
return values

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38 changes: 31 additions & 7 deletions pandas/core/indexes/period.py
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Expand Up @@ -17,6 +17,7 @@
is_float_dtype,
is_integer,
is_integer_dtype,
is_object_dtype,
pandas_dtype,
)

Expand Down Expand Up @@ -594,13 +595,13 @@ def get_indexer_non_unique(self, target):
return ensure_platform_int(indexer), missing

def _get_unique_index(self, dropna=False):
"""
wrap Index._get_unique_index to handle NaT
"""
res = super()._get_unique_index(dropna=dropna)
if dropna:
res = res.dropna()
return res
if self.is_unique and not dropna:
return self

result = self._data.unique()
if dropna and self.hasnans:
result = result[~result.isna()]
return self._shallow_copy(result)

def get_loc(self, key, method=None, tolerance=None):
"""
Expand Down Expand Up @@ -818,6 +819,29 @@ def intersection(self, other, sort=False):
result = self._shallow_copy(np.asarray(i8result, dtype=np.int64), name=res_name)
return result

def difference(self, other, sort=None):
self._validate_sort_keyword(sort)
self._assert_can_do_setop(other)
res_name = get_op_result_name(self, other)
other = ensure_index(other)

if self.equals(other):
# pass an empty PeriodArray with the appropriate dtype
return self._shallow_copy(self._data[:0])

if is_object_dtype(other):
return self.astype(object).difference(other).astype(self.dtype)

elif not is_dtype_equal(self.dtype, other.dtype):
return self

i8self = Int64Index._simple_new(self.asi8)
i8other = Int64Index._simple_new(other.asi8)
i8result = i8self.difference(i8other, sort=sort)

result = self._shallow_copy(np.asarray(i8result, dtype=np.int64), name=res_name)
return result

# ------------------------------------------------------------------------

def _apply_meta(self, rawarr):
Expand Down