⚡️ Speed up function capture_code_cell by 6%

[codeflash-ai]

📄 6% (0.06x) speedup for capture_code_cell in panel/io/handlers.py

⏱️ Runtime : 1.97 milliseconds → 1.86 milliseconds (best of 55 runs)

📝 Explanation and details

The optimized code achieves a 6% speedup through three key optimizations that reduce redundant string operations:

1. Conditional String Replacements
The original code performed replace() operations on every source line, even when the target strings weren't present. The optimization adds a conditional check (if 'get_ipython().run_line_magic' in line or 'get_ipython().magic' in line:) before performing replacements. This eliminates unnecessary string operations on the majority of lines that don't contain magic commands.

2. Cached String Stripping
The original code called cell_out.strip() multiple times - once in the parsing loop condition and again when checking for semicolons. The optimization caches this result in cell_out_strip and reuses it, eliminating redundant strip() calls.

3. Simplified String Concatenation
The original code used a multi-line triple-quoted f-string for the output capture code, which creates multiple string objects. The optimization replaces this with direct f-string concatenation, reducing memory allocations during string construction.

Performance Impact by Test Case:

• Large cells with many lines (1000+ lines): 24-30% faster due to the conditional replacement optimization
• Cells with magic commands: Modest improvements as only relevant lines are processed
• Standard small cells: 1-3% improvements from cached stripping and string optimizations
• Edge cases: Minimal impact, maintaining same functionality

The optimizations are most effective for large cells with many non-magic lines, where the conditional replacement check provides the biggest benefit by avoiding thousands of unnecessary string operations.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	✅ 13 Passed
🌀 Generated Regression Tests	✅ 48 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

⚙️ Existing Unit Tests and Runtime

Test File::Test Function	Original ⏱️	Optimized ⏱️	Speedup
io/test_handlers.py::test_capture_code_cell_expression	21.8μs	21.1μs	3.27%✅
io/test_handlers.py::test_capture_code_cell_expression_semicolon	14.7μs	14.8μs	-0.434%⚠️
io/test_handlers.py::test_capture_code_cell_expression_with_comment	22.2μs	21.8μs	1.93%✅
io/test_handlers.py::test_capture_code_cell_function	42.7μs	41.0μs	4.01%✅
io/test_handlers.py::test_capture_code_cell_loop	40.4μs	40.1μs	0.710%✅
io/test_handlers.py::test_capture_code_cell_multi_line_expression	43.9μs	43.5μs	0.705%✅
io/test_handlers.py::test_capture_code_cell_statement	16.2μs	15.7μs	3.44%✅
io/test_handlers.py::test_capture_code_expression_multi_line_with_comment	39.3μs	39.9μs	-1.60%⚠️

🌀 Generated Regression Tests and Runtime

from __future__ import annotations

import ast
import logging

# imports
import pytest
from panel.io.handlers import capture_code_cell

log = logging.getLogger('panel.io.handlers')
from panel.io.handlers import capture_code_cell

# unit tests

# ---- Basic Test Cases ----

def test_empty_source_returns_empty_list():
    # Should return empty list for empty cell source
    cell = {'id': 'cell1', 'source': ''}
    codeflash_output = capture_code_cell(cell) # 567ns -> 591ns (4.06% slower)

def test_single_expression_captured():
    # Should wrap a single expression in output capture code
    cell = {'id': 'cell2', 'source': '1+2'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 19.1μs -> 18.6μs (2.79% faster)

def test_single_statement_no_capture():
    # Should not wrap assignment statement in output capture code
    cell = {'id': 'cell3', 'source': 'x = 5'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 20.4μs -> 19.9μs (2.31% faster)

def test_multiple_lines_last_expression_capture():
    # Only the last expression should be wrapped
    cell = {'id': 'cell4', 'source': 'x = 5\ny+2'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 18.0μs -> 17.8μs (0.949% faster)

def test_multiple_lines_last_statement_no_capture():
    # Last line is a statement, so no output capture
    cell = {'id': 'cell5', 'source': 'x = 5\ny = 2'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 19.3μs -> 18.9μs (1.87% faster)

def test_semicolon_at_end_no_capture():
    # If the last line ends with a semicolon, do not wrap in output capture
    cell = {'id': 'cell6', 'source': 'x = 5;'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 12.9μs -> 13.1μs (1.37% slower)

def test_magic_line_removed():
    # Should remove get_ipython().run_line_magic from non-final lines
    cell = {'id': 'cell7', 'source': 'get_ipython().run_line_magic("matplotlib", "inline")\nx = 1\nx'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 16.1μs -> 16.1μs (0.467% faster)

# ---- Edge Test Cases ----

def test_invalid_python_skipped():
    # Should skip cell with invalid syntax
    cell = {'id': 'cell8', 'source': 'x = '}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 65.1μs -> 65.5μs (0.734% slower)

def test_comment_line_removal():
    # Should remove comments from single-line expressions
    cell = {'id': 'cell9', 'source': '1+2 # sum'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 22.8μs -> 23.0μs (0.996% slower)

def test_comment_in_string_not_removed():
    # Should not remove comments inside string literals
    cell = {'id': 'cell10', 'source': 'a = "#notacomment"'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 25.5μs -> 25.0μs (1.69% faster)

def test_multiline_expression_parsing():
    # Should expand multiline expressions until parsable
    cell = {'id': 'cell11', 'source': '(\n1+\n2\n)'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 42.5μs -> 44.0μs (3.46% slower)

def test_multiline_comment_not_removed():
    # Should not remove comments from multiline code
    cell = {'id': 'cell12', 'source': 'x = 1\n# comment\ny = 2'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 18.3μs -> 18.1μs (0.766% faster)

def test_blank_lines_in_cell():
    # Should handle blank lines gracefully
    cell = {'id': 'cell13', 'source': '\n\nx = 1\n\n'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 20.3μs -> 19.4μs (4.30% faster)

def test_cell_with_only_comment():
    # Should skip cell with only a comment
    cell = {'id': 'cell14', 'source': '# just a comment'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 13.8μs -> 13.5μs (2.34% faster)

def test_cell_with_whitespace_only():
    # Should skip cell with only whitespace
    cell = {'id': 'cell15', 'source': '   '}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 42.1μs -> 42.5μs (1.07% slower)

def test_cell_with_expression_and_semicolon():
    # If expression ends with semicolon, do not wrap in output capture
    cell = {'id': 'cell16', 'source': '1+2;'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 14.8μs -> 14.8μs (0.149% slower)

def test_cell_with_hash_color_code():
    # Should not remove hex color codes
    cell = {'id': 'cell17', 'source': 'color = "#000000"'}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 27.7μs -> 28.6μs (3.26% slower)

# ---- Large Scale Test Cases ----

def test_large_cell_with_many_lines():
    # Should handle cells with many lines efficiently
    lines = [f'x{i} = {i}' for i in range(999)]
    cell = {'id': 'cell18', 'source': '\n'.join(lines + ['x998'])}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 87.9μs -> 67.6μs (30.0% faster)
    for i in range(998):
        pass

def test_large_cell_with_only_assignments():
    # Should not wrap any lines in output capture if all are assignments
    lines = [f'x{i} = {i}' for i in range(1000)]
    cell = {'id': 'cell19', 'source': '\n'.join(lines)}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 91.4μs -> 71.5μs (27.9% faster)
    for i in range(1000):
        pass

def test_large_cell_with_expressions():
    # Should wrap only the last expression in output capture
    lines = [f'x{i} = {i}' for i in range(999)]
    cell = {'id': 'cell20', 'source': '\n'.join(lines + ['x998 + 1'])}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 89.9μs -> 70.1μs (28.3% faster)
    for i in range(998):
        pass

def test_large_cell_with_magic_and_comments():
    # Should remove magic and comments in large cells
    lines = ['get_ipython().run_line_magic("foo", "bar")'] + [f'x{i} = {i} # comment' for i in range(998)]
    cell = {'id': 'cell21', 'source': '\n'.join(lines + ['x997 + 2 # sum'])}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 107μs -> 86.8μs (24.4% faster)

def test_large_cell_with_blank_lines_and_comments():
    # Should handle large cells with blank lines and comments
    lines = [''] * 10 + [f'x{i} = {i} # comment' for i in range(980)] + ['x979']
    cell = {'id': 'cell22', 'source': '\n'.join(lines)}
    codeflash_output = capture_code_cell(cell); out = codeflash_output # 96.4μs -> 77.6μs (24.3% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.
#------------------------------------------------
from __future__ import annotations

import ast
import logging

# imports
import pytest  # used for our unit tests
from panel.io.handlers import capture_code_cell

log = logging.getLogger('panel.io.handlers')
from panel.io.handlers import capture_code_cell

# unit tests

# --- BASIC TEST CASES ---

def test_empty_source_returns_empty_list():
    # Test when cell source is empty
    cell = {'source': '', 'id': 'cell1'}
    codeflash_output = capture_code_cell(cell) # 604ns -> 622ns (2.89% slower)

def test_single_expression_captures_output():
    # Test a cell with a single expression
    cell = {'source': '2 + 2', 'id': 'cell2'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 19.3μs -> 19.2μs (0.755% faster)

def test_single_statement_returns_statement():
    # Test a cell with a single statement
    cell = {'source': 'x = 5', 'id': 'cell3'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 20.5μs -> 20.6μs (0.514% slower)

def test_multiple_lines_last_expression_captured():
    # Test a cell with several lines, ending in an expression
    cell = {'source': 'a = 1\nb = 2\nb + a', 'id': 'cell4'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 17.6μs -> 17.8μs (0.866% slower)

def test_multiple_lines_last_statement():
    # Test a cell with several lines, ending in a statement
    cell = {'source': 'a = 1\nb = 2\nc = a + b', 'id': 'cell5'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 20.2μs -> 20.3μs (0.547% slower)

def test_magic_line_stripped():
    # Test a cell with IPython magic invocation
    cell = {'source': 'get_ipython().run_line_magic("matplotlib", "inline")\n2 + 2', 'id': 'cell6'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 17.9μs -> 18.0μs (0.611% slower)

def test_magic_and_statement():
    # Test a cell with magic and a statement
    cell = {'source': 'get_ipython().magic("matplotlib inline")\nx = 42', 'id': 'cell7'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 19.4μs -> 20.2μs (3.61% slower)

# --- EDGE TEST CASES ---

def test_cell_with_only_comment():
    # Test a cell containing only a comment
    cell = {'source': '# just a comment', 'id': 'cell8'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 14.3μs -> 14.1μs (1.68% faster)

def test_cell_with_comment_and_expression():
    # Test a cell with an expression and a comment
    cell = {'source': '2 + 2 # add two numbers', 'id': 'cell9'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 21.5μs -> 21.8μs (1.39% slower)

def test_cell_with_hex_color_comment():
    # Test a cell with a comment that looks like a hex color
    cell = {'source': 'color = "#000000" # black', 'id': 'cell10'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 26.1μs -> 26.9μs (2.76% slower)

def test_cell_with_semicolon_expression():
    # Test a cell ending in a semicolon (should not capture output)
    cell = {'source': '2 + 2;', 'id': 'cell11'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 12.4μs -> 12.5μs (1.14% slower)

def test_cell_with_semicolon_statement():
    # Test a cell with a statement ending in semicolon
    cell = {'source': 'x = 2;', 'id': 'cell12'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 12.8μs -> 13.5μs (4.95% slower)

def test_cell_with_invalid_python():
    # Test a cell with invalid Python syntax
    cell = {'source': 'for', 'id': 'cell13'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 63.9μs -> 64.8μs (1.39% slower)

def test_cell_with_blank_lines_and_expression():
    # Test a cell with blank lines and an expression
    cell = {'source': '\n\n2 + 2\n', 'id': 'cell14'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 20.6μs -> 20.9μs (1.44% slower)

def test_cell_with_multiline_comment():
    # Test a cell with a multiline comment
    cell = {'source': '"""This is a comment"""\n2 + 2', 'id': 'cell15'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 17.7μs -> 17.1μs (3.36% faster)

def test_cell_with_expression_and_multiple_comments():
    # Test a cell with expression and multiple comments
    cell = {'source': '2 + 2 # first comment # second comment', 'id': 'cell16'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 21.0μs -> 20.6μs (1.94% faster)

def test_cell_with_only_whitespace():
    # Test a cell with only whitespace
    cell = {'source': '   \n  \n', 'id': 'cell17'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 43.5μs -> 44.0μs (1.08% slower)

def test_cell_with_non_ascii_characters():
    # Test a cell containing non-ascii characters
    cell = {'source': 'text = "café"\ntext', 'id': 'cell18'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 18.6μs -> 18.2μs (2.45% faster)

def test_cell_with_last_line_unparsable_but_previous_lines_make_valid():
    # Test a cell where the last line is invalid, but combining with previous lines is valid
    cell = {'source': 'def f():\n    return 1', 'id': 'cell19'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 38.9μs -> 39.3μs (0.961% slower)

# --- LARGE SCALE TEST CASES ---

def test_large_cell_with_many_statements_and_expression():
    # Test a cell with many statements and a final expression
    lines = [f'x{i} = {i}' for i in range(50)] + ['x0 + x49']
    cell = {'source': '\n'.join(lines), 'id': 'cell20'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 23.4μs -> 23.3μs (0.426% faster)
    for i in range(50):
        pass

def test_large_cell_with_many_statements_only():
    # Test a cell with many statements, no output
    lines = [f'x{i} = {i}' for i in range(100)]
    cell = {'source': '\n'.join(lines), 'id': 'cell21'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 30.5μs -> 27.7μs (10.1% faster)
    for i in range(100):
        pass

def test_large_cell_with_magic_and_expressions():
    # Test a cell with many magics and a final expression
    lines = ['get_ipython().run_line_magic("foo", "bar")' for _ in range(20)] + ['a = 1', 'b = 2', 'a + b']
    cell = {'source': '\n'.join(lines), 'id': 'cell22'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 21.8μs -> 22.8μs (4.78% slower)
    # No magic lines should remain
    for line in result:
        pass

def test_large_cell_with_long_expression():
    # Test a cell with a very long expression
    expr = '+'.join([f'x{i}' for i in range(200)])
    cell = {'source': expr, 'id': 'cell23'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 271μs -> 265μs (2.56% faster)

def test_large_cell_with_comments_and_statements():
    # Test a cell with many statements, each with a comment
    lines = [f'x{i} = {i} # comment {i}' for i in range(50)]
    cell = {'source': '\n'.join(lines), 'id': 'cell24'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 32.6μs -> 31.1μs (4.97% faster)
    for i in range(50):
        pass

def test_large_cell_with_blank_lines_and_expression():
    # Test a cell with many blank lines interspersed
    lines = [''] * 20 + ['x = 1', 'y = 2', 'x + y'] + [''] * 20
    cell = {'source': '\n'.join(lines), 'id': 'cell25'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 27.4μs -> 25.6μs (6.96% faster)

def test_large_cell_with_non_ascii_and_expression():
    # Test a cell with non-ascii characters and a final expression
    lines = [f'text{i} = "café{i}"' for i in range(10)] + ['text0 + text9']
    cell = {'source': '\n'.join(lines), 'id': 'cell26'}
    codeflash_output = capture_code_cell(cell); result = codeflash_output # 20.2μs -> 19.7μs (2.31% faster)
    for i in range(10):
        pass
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-capture_code_cell-mhbm4s9n and push.