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BUG: ArrayManager reindex with copy=True not copying #42647

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Merged
merged 6 commits into from
Aug 4, 2021
Merged

BUG: ArrayManager reindex with copy=True not copying #42647

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58a1244
BUG: ArrayManager reindex with copy=True not copying
jbrockmendel Jul 21, 2021
6e8d575
Merge branch 'master' into perf-reindex
jbrockmendel Jul 28, 2021
e2c8b2e
test case passing both index and columns
jbrockmendel Jul 28, 2021
e2f5598
Merge branch 'master' into perf-reindex
jbrockmendel Jul 29, 2021
7262ba2
Merge branch 'master' into perf-reindex
jbrockmendel Jul 30, 2021
13a6ab6
Merge remote-tracking branch 'upstream/master' into perf-reindex
jbrockmendel Jul 30, 2021
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2 changes: 2 additions & 0 deletions pandas/core/generic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4831,6 +4831,8 @@ def _reindex_axes(
copy=copy,
allow_dups=False,
)
# If we've made a copy once, no need to make another one
copy = False

return obj

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2 changes: 2 additions & 0 deletions pandas/core/internals/array_manager.py
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Expand Up @@ -610,6 +610,8 @@ def _reindex_indexer(
)
else:
arr = self.arrays[i]
if copy:
arr = arr.copy()
new_arrays.append(arr)

else:
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14 changes: 14 additions & 0 deletions pandas/tests/frame/methods/test_reindex.py
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Expand Up @@ -83,6 +83,20 @@ class TestDataFrameSelectReindex:
# These are specific reindex-based tests; other indexing tests should go in
# test_indexing

def test_reindex_copies(self):
# based on asv time_reindex_axis1
N = 10
df = DataFrame(np.random.randn(N * 10, N))
cols = np.arange(N)
np.random.shuffle(cols)

result = df.reindex(columns=cols, copy=True)
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can you check with both axis reindexing as well (result should be the same) e.g. only a single copy.

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do you mean calling df.reindex(index=foo, copy=True)? that's covered by existing tests. this test should be focused on the particular bug

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yeah actually meant calling them both (columns AND index)

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updated + greenish

assert not np.shares_memory(result[0]._values, df[0]._values)

# pass both columns and index
result2 = df.reindex(columns=cols, index=df.index, copy=True)
assert not np.shares_memory(result2[0]._values, df[0]._values)

def test_reindex_date_fill_value(self):
# passing date to dt64 is deprecated
arr = date_range("2016-01-01", periods=6).values.reshape(3, 2)
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