Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

ENH/CoW: use lazy copy in set_index method #49557

Merged
merged 3 commits into from
Nov 15, 2022
Merged

ENH/CoW: use lazy copy in set_index method #49557

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
5c9e917
use lazy copy on set_index methd
ntachukwu Nov 6, 2022
345db89
improve test
ntachukwu Nov 9, 2022
6c906d8
pre commit test file (my bad)
ntachukwu Nov 9, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 2 additions & 1 deletion pandas/core/frame.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5855,7 +5855,8 @@ def set_index(
if inplace:
frame = self
else:
frame = self.copy()
# GH 49473 Use "lazy copy" with Copy-on-Write
frame = self.copy(deep=None)

arrays = []
names: list[Hashable] = []
Expand Down
17 changes: 17 additions & 0 deletions pandas/tests/copy_view/test_methods.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -214,3 +214,20 @@ def test_chained_methods(request, method, idx, using_copy_on_write):
df.iloc[0, 0] = 0
if not df2_is_view:
tm.assert_frame_equal(df2.iloc[:, idx:], df_orig)


def test_set_index(using_copy_on_write):
# GH 49473
df = DataFrame({"a": [1, 2, 3], "b": [4, 5, 6], "c": [0.1, 0.2, 0.3]})
df_orig = df.copy()
df2 = df.set_index("a")

if using_copy_on_write:
assert np.shares_memory(get_array(df2, "b"), get_array(df, "b"))
else:
assert not np.shares_memory(get_array(df2, "b"), get_array(df, "b"))

# mutating df2 triggers a copy-on-write for that column / block
df2.iloc[0, 1] = 0
assert not np.shares_memory(get_array(df2, "c"), get_array(df, "c"))
tm.assert_frame_equal(df, df_orig)