[Fix] Support trace-specific color sequences in Plotly Express via templates by antonymilne · Pull Request #5437 · plotly/plotly.py

antonymilne

added 5 commits

November 26, 2025 17:01

- Check template.data.<trace_type> for marker.color or line.color before falling back to template.layout.colorway
- Handle timeline special case (maps to bar trace type)
- Use marker colors first, fall back to line colors if no markers found
- Fixes issue plotly#5416

- Modify apply_default_cascade to check template.data.<trace_type> for marker.color or line.color
- Fallback to template.layout.colorway if trace-specific colors not found
- Add comprehensive tests for trace-specific color sequences
- Handle timeline special case (maps to bar trace type)
- Follow existing patterns for symbol_sequence and line_dash_sequence

Fixes plotly#5416

- Modify apply_default_cascade to read colors from template.data.<trace_type>
- Prioritize trace-specific colors over layout.colorway
- Add special case for timeline constructor (maps to bar trace type)
- Add comprehensive tests for trace-specific color sequences
- Test trace type isolation, fallback behavior, and timeline special case

antonymilne changed the title ~~Trace-specific colors~~ [Fix] Support trace-specific color sequences in Plotly Express via templates

Dec 1, 2025

- Make constructor parameter required (was optional with None default)
- Refactor trace-specific color extraction to only assign when colors are found
- Improve code clarity by checking for non-empty color list before assignment

- Remove redundant check that was setting color_discrete_sequence to None
- The check is unnecessary since we only assign trace_specific_colors when any() is True
- Fallback logic to layout.colorway and qualitative.D3 remains intact

Co-authored-by: Emily KL <4672118+emilykl@users.noreply.github.com>