Copy receiver_data in autoimpute to avoid mutating caller's frame#185
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Copy receiver_data in autoimpute to avoid mutating caller's frame#185
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autoimpute ended with
receiver_data[var] = median_imputations[var]
which could write through to the caller's original DataFrame depending
on whether intermediate pandas operations returned a copy or a view.
This is a silent side effect: the user's input frame would gain new
columns without any notification.
Take a defensive .copy() of receiver_data at the top of autoimpute so
the caller's frame is always preserved. The imputed columns are
returned exclusively via result.receiver_data.
Tests
- test_autoimpute_does_not_mutate_caller_receiver asserts that
receiver_data passed in remains pristine and the returned frame
carries the imputed column.
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MaxGhenis
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Apr 17, 2026
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MaxGhenis
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autoimpute defensive copy verified:
receiver_data = receiver_data.copy()at function entry before any preprocessing.- Test asserts caller's snapshot is untouched (
pd.testing.assert_frame_equal(receiver, snapshot),'y' not in receiver.columns) while the returnedresult.receiver_datacarries the imputed column. - Performance: single O(N) copy at entry is negligible vs the multiple intermediate frames autoimpute already allocates per model × quantile during imputation.
CI all green. Mergeable. LGTM.
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Summary
Fixes finding #13.
autoimputeended withreceiver_data[var] = median_imputations[var], which could write through to the caller's original DataFrame depending on whether intermediate pandas operations returned a copy or a view. The caller's input frame could silently gain new columns without notification.Take a defensive
.copy()at the top ofautoimputeso the caller's frame is always preserved; imputed columns are returned exclusively viaresult.receiver_data.Test plan
test_autoimpute_does_not_mutate_caller_receiver: caller'sreceiver_datastays pristine, returnedresult.receiver_datahas the imputed column.