Fix performance of streaming long text#14941
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krassowski merged 3 commits intoipython:mainfrom Aug 6, 2025
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Pull Request Overview
This PR fixes a performance issue when streaming long text output by changing the internal data structure from string concatenation to list accumulation. The change addresses issue #14937 where streaming large amounts of text was inefficient due to repeated string reallocation.
Key changes:
- Replaces string concatenation with list accumulation for stream data
- Updates type annotations to reflect the new data structure
- Adds a performance test to verify the fix
Reviewed Changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| tests/test_interactiveshell.py | Adds performance test for streaming operations |
| IPython/core/magics/basic.py | Updates notebook output handling to work with list-based stream data |
| IPython/core/interactiveshell.py | Changes stream data accumulation from string concatenation to list appending |
| IPython/core/history.py | Updates type annotation for bundle to support both string and list types |
Comments suppressed due to low confidence (1)
tests/test_interactiveshell.py:95
- The performance test only verifies that execution completes within 10 seconds but doesn't validate that the output is correct. Consider adding an assertion to verify that the expected output (numbers 0-249999) is actually produced.
assert duration < 10
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|
This looks good! Thanks 🙌 |
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Fixes #14937
CC @Darshan808