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⚡️ Speed up function fix_nan_category by 137%
#30
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⚡️ Speed up function fix_nan_category by 137%
#30
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The optimized version achieves a **137% speedup** by eliminating unnecessary work through two key optimizations: **What was optimized:** 1. **Pre-filtered categorical detection**: Instead of checking `column.dtype.name == "category"` for every column in the loop, the optimization identifies all categorical columns upfront using `enumerate(df.dtypes)` and stores their indices. 2. **Early exit for non-categorical DataFrames**: Added a guard clause that returns immediately if no categorical columns exist, avoiding any loop overhead. **Why this is faster:** - **Reduced dtype access overhead**: The original code called `df.iloc[:, i]` (expensive pandas indexing) for every column, then checked its dtype. The optimization accesses `df.dtypes` once, which is much faster than repeated `iloc` calls. - **Eliminated wasted iterations**: For DataFrames with few/no categorical columns, the original code still iterates through all columns. The optimization skips non-categorical columns entirely and exits early when possible. **Performance characteristics from tests:** - **Large DataFrames with mixed types**: Shows significant gains (16-22% faster) when many columns exist but only some are categorical - **No categorical columns**: Dramatic improvement (33-58% faster) due to early exit - **Small DataFrames**: Slight overhead (9-16% slower) due to upfront processing, but this is negligible in absolute terms (microseconds) The line profiler confirms this: the original spent 66.8% of time on `df.iloc` access across all columns, while the optimized version only accesses iloc for the pre-identified categorical columns, reducing this bottleneck substantially.
📝 WalkthroughWalkthroughThe Sequence Diagram(s)mermaid mermaid Pre-merge checks❌ Failed checks (1 warning)
✅ Passed checks (2 passed)
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Actionable comments posted: 1
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📒 Files selected for processing (1)
deepnote_toolkit/ocelots/pandas/utils.py(1 hunks)
🔇 Additional comments (1)
deepnote_toolkit/ocelots/pandas/utils.py (1)
24-29: Solid optimization: pre-filter and early exit.Pre-collecting categorical indices and returning early when none exist avoids wasted iteration. Correct approach.
| for i in categorical_indices: | ||
| column = df.iloc[:, i] | ||
| df.iloc[:, i] = column.cat.add_categories("nan") |
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🧹 Nitpick | 🔵 Trivial
Minor: simplify the assignment.
Lines 33-34 can be combined into one statement without the intermediate variable.
for i in categorical_indices:
- column = df.iloc[:, i]
- df.iloc[:, i] = column.cat.add_categories("nan")
+ df.iloc[:, i] = df.iloc[:, i].cat.add_categories("nan")📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| for i in categorical_indices: | |
| column = df.iloc[:, i] | |
| df.iloc[:, i] = column.cat.add_categories("nan") | |
| for i in categorical_indices: | |
| df.iloc[:, i] = df.iloc[:, i].cat.add_categories("nan") |
🤖 Prompt for AI Agents
In deepnote_toolkit/ocelots/pandas/utils.py around lines 32 to 34, the code uses
an intermediate variable 'column' to add a category; simplify by replacing the
two statements with a single assignment that updates the DataFrame column in
place, e.g. assign the result of df.iloc[:, i].cat.add_categories("nan")
directly back to df.iloc[:, i].
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Actionable comments posted: 1
♻️ Duplicate comments (1)
deepnote_toolkit/ocelots/pandas/utils.py (1)
45-47: Intermediate variable still present.Past review suggested combining lines 46-47 into a single statement. The intermediate variable remains.
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📒 Files selected for processing (1)
deepnote_toolkit/ocelots/pandas/utils.py(1 hunks)
🔇 Additional comments (2)
deepnote_toolkit/ocelots/pandas/utils.py (2)
41-42: Early exit is correct.Avoids wasted iterations when no categorical columns exist. Validated by benchmark improvements.
36-48: Optimization logic is sound, but manual verification needed.Pre-collection of categorical indices and early exit avoid repeated dtype checks. However, edge case testing couldn't run in this environment (pandas unavailable). Manually verify behavior with empty DataFrames and non-categorical inputs to confirm the early exit and iloc assignment work correctly across your pandas version.
| categorical_indices = [ | ||
| i for i, dtype in enumerate(df.dtypes) if dtype.name == "category" | ||
| ] |
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🧹 Nitpick | 🔵 Trivial
Consider using pandas API for dtype checking.
dtype.name == "category" works but pd.api.types.is_categorical_dtype(dtype) is more idiomatic and robust.
categorical_indices = [
- i for i, dtype in enumerate(df.dtypes) if dtype.name == "category"
+ i for i, dtype in enumerate(df.dtypes) if pd.api.types.is_categorical_dtype(dtype)
]🤖 Prompt for AI Agents
In deepnote_toolkit/ocelots/pandas/utils.py around lines 38 to 40, replace the
dtype name string comparison with the pandas API for checking categorical
dtypes: use pd.api.types.is_categorical_dtype(dtype) when filtering df.dtypes so
detection is more idiomatic and robust; update the list comprehension
accordingly and ensure pd.api.types is imported/accessible in the module.
📄 137% (1.37x) speedup for
fix_nan_categoryindeepnote_toolkit/ocelots/pandas/utils.py⏱️ Runtime :
834 milliseconds→352 milliseconds(best of10runs)📝 Explanation and details
The optimized version achieves a 137% speedup by eliminating unnecessary work through two key optimizations:
What was optimized:
column.dtype.name == "category"for every column in the loop, the optimization identifies all categorical columns upfront usingenumerate(df.dtypes)and stores their indices.Why this is faster:
df.iloc[:, i](expensive pandas indexing) for every column, then checked its dtype. The optimization accessesdf.dtypesonce, which is much faster than repeatediloccalls.Performance characteristics from tests:
The line profiler confirms this: the original spent 66.8% of time on
df.ilocaccess across all columns, while the optimized version only accesses iloc for the pre-identified categorical columns, reducing this bottleneck substantially.✅ Correctness verification report:
🌀 Generated Regression Tests and Runtime
⏪ Replay Tests and Runtime
test_pytest_testsunittest_dataframe_browser_py_testsunittest_config_py_testsunittest_runtime_executor_py___replay_test_0.py::test_deepnote_toolkit_ocelots_pandas_utils_fix_nan_categorytest_pytest_testsunittest_xdg_paths_py_testsunittest_jinjasql_utils_py_testsunittest_url_utils_py_testsun__replay_test_0.py::test_deepnote_toolkit_ocelots_pandas_utils_fix_nan_categoryTo edit these changes
git checkout codeflash/optimize-fix_nan_category-mhmv7xt8and push.Summary by CodeRabbit