# profiling.sampling --- Statistical profiler — Heatmap format

> Heatmap format (--heatmap) generates an interactive HTML visualization showing sample counts at the source line level python -m profiling.sampling run --heatmap script.py python -m profiling.sampling run --heatmap -o my_heatmap script.py alt: Tachyon heatmap visualization :align: center :width: 100%

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- Canonical URL: <https://wikikv.com/k/ref-python-f5da1affae550e0828db>
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- Updated: `2026-08-16T09:32:07.077008+00:00`
- Tags: `reference-seed`, `python`, `library`, `profiling`, `sampling`, `statistical`, `profiler`, `heatmap`, `format`

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Heatmap format (--heatmap) generates an interactive HTML visualization showing sample counts at the source line level

python -m profiling.sampling run --heatmap script.py python -m profiling.sampling run --heatmap -o my_heatmap script.py

alt: Tachyon heatmap visualization :align: center :width: 100%

The heatmap overlays sample counts directly on your source code. Lines are color-coded from cool (few samples) to hot (many samples). Navigation buttons (▲▼) let you jump between callers and callees.

Unlike other formats that produce a single file, heatmap output creates a directory containing HTML files for each profiled source file. If no output path is specified, the directory is named heatmap_PID.

The heatmap visualization displays your source code with a color gradient indicating how many samples were collected at each line. Hot lines (many samples) appear in warm colors, while cold lines (few or no samples) appear in cool colors. This view helps pinpoint exactly which lines of code are responsible for time consumption.

The heatmap interface provides several interactive features

Coloring modes: toggle between "Self Time" (direct execution) and "Total Time" (cumulative, including time in called functions) Cold code filtering: show all lines or only lines with samples Call graph navigation: each line shows navigation buttons (▲ for callers, ▼ for callees) that let you trace execution paths through your code. When multiple functions called or were called from a line, a menu appears showing all options with their sample counts. Scroll minimap: a vertical overview showing the heat distribution across the entire file Hierarchical index: files organized by type (stdlib, site-packages, project) with aggregate sample counts per folder Dark/light theme: toggle with preference saved across sessions Line linking: click line numbers to create shareable URLs

When opcode-level profiling is enabled with --opcodes, each hot line can be expanded to show which bytecode instructions consumed time

alt: Heatmap with expanded bytecode panel :align: center :width: 100%

Expanding a hot line reveals the bytecode instructions executed, including specialized variants. The panel shows sample counts per instruction and the overall specialization percentage for the line.

Try the interactive example _! …

Attribution: Adapted from Python Documentation under PSF-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.