Data precision

A data file states its numbers to a definite number of digits, and that is a claim. 0.3333 says a coordinate is known to about 1e-4 of a cell edge; 0.33 says only 1e-2. httk records that claim and uses it, so a matching tolerance or an spglib symprec follows the data instead of being a constant somebody guessed.

from httk.atomistic import structure_tolerance
from httk.core import load

asu = load("measured.cif")
asu.coordinate_precision      # Fraction(1, 10000) — from the file's own digits
structure_tolerance(asu)      # a matching tolerance derived from the data

The full guide, Data precision in detail, covers exactly what is recorded, where precision comes from (digits, stated esds, format defaults), what it is used for, and how it is served over OPTIMADE.