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BUG: avoid incorrectly inheriting result #27445

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BUG: avoid incorrectly inheriting result #27445

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17 changes: 11 additions & 6 deletions pandas/core/groupby/generic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -143,8 +143,12 @@ def _cython_agg_blocks(self, how, alt=None, numeric_only=True, min_count=-1):
new_blocks = []
new_items = []
deleted_items = []
no_result = object()
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why don't you just set result = None outside the try instead as its more clear

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because I don't know for sure that None won't be the correct result produced on line 154

for block in data.blocks:

# avoid inheriting result from previous step in loop
result = no_result

locs = block.mgr_locs.as_array
try:
result, _ = self.grouper.aggregate(
Expand All @@ -171,15 +175,16 @@ def _cython_agg_blocks(self, how, alt=None, numeric_only=True, min_count=-1):
except TypeError:
# we may have an exception in trying to aggregate
# continue and exclude the block
pass
deleted_items.append(locs)
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do we actually use the deleted_items?

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yes, down on 195

continue

finally:
if result is not no_result:
dtype = block.values.dtype

dtype = block.values.dtype

# see if we can cast the block back to the original dtype
result = block._try_coerce_and_cast_result(result, dtype=dtype)
newb = block.make_block(result)
# see if we can cast the block back to the original dtype
result = block._try_coerce_and_cast_result(result, dtype=dtype)
newb = block.make_block(result)

new_items.append(locs)
new_blocks.append(newb)
Expand Down