Module numfmt 

Display-time number formatting: digit grouping (thousands separators), decimal separator choice, and optional fixed float precision.

This is display-only. Exports, queries, filter values, views, and group-by key strings always use raw values — see format_any_value call sites. Nothing here is ever fed back into Polars.

Performance

Formatting runs once per visible cell per frame (roughly visible_rows * visible_cols), so the hot path is deliberately allocation free beyond the destination String the caller already needs:

• Integers are written digit-by-digit into a stack buffer with separators emitted inline — one pass, no intermediate string.
• NumberFormat::width_i64 computes display width arithmetically, so the locked-column measurement pass never builds a string it throws away.
• Per-column decisions (dtype eligibility, exclude globs) resolve to a CellFormatter once per column per frame, never per cell.

Structs

Glob

Minimal glob matcher supporting * (any run) and ? (one character).

NumberFormat

How numbers are rendered. Resolved from config once at load time.

NumberFormatSettings

Fully resolved display-formatting settings, held in the render context.

Enums

CellFormatter

Per-column formatting decision, resolved once per column per frame.

Grouping

Digit grouping style.

Functions

display_width

Cells a value takes on screen without building its string, where possible.

format_any_value

Format one Polars value for display.

group_chrome

Comma-group a count for the application’s own chrome — the control bar’s row count, info-panel totals, and similar labels.

is_numeric_dtype

True for dtypes whose values are numbers we group.

is_right_aligned_dtype

True for dtypes that should render flush-right in the data table.

preset_for_locale_tag

Map a POSIX locale / language tag to the preset whose conventions match.

system_locale_tag

Read the environment’s numeric locale, honouring POSIX precedence. Returns None when unset or explicitly the C/POSIX locale.