Molecular Descriptors

COSMolKit exposes the source-backed molecular descriptor functions from the Rust core directly in Python. Descriptor calls are read-only and do not mutate the input cosmolkit.Molecule.

The descriptor surface is experimental. Supported rows are compared field-by-field, including exact floating-point bit patterns, against pinned RDKit golden data. A source state outside the modeled boundary raises NotImplementedError instead of returning an approximate value.

Basic Descriptors

import cosmolkit

molecule = cosmolkit.Molecule.from_smiles("c1ccccc1O")

formula = cosmolkit.calc_mol_formula(molecule)
average_weight = cosmolkit.calc_mol_wt(molecule)
exact_weight = cosmolkit.calc_exact_mol_wt(molecule)
aromatic_rings = cosmolkit.calc_num_aromatic_rings(molecule)

print(formula, average_weight, exact_weight, aromatic_rings)

The complete public descriptor set is:

• cosmolkit.calc_mol_wt()

• cosmolkit.calc_exact_mol_wt()

• cosmolkit.calc_mol_formula()

• cosmolkit.calc_num_hbd()

• cosmolkit.calc_num_hba()

• cosmolkit.calc_fraction_csp3()

• cosmolkit.calc_crippen_descriptors()

• cosmolkit.calc_tpsa()

• cosmolkit.calc_num_aromatic_rings()

• cosmolkit.calc_num_rotatable_bonds()

• cosmolkit.calc_qed()

Formula Options

calc_mol_formula() accepts separate_isotopes and abbreviate_h_isotopes. When isotope separation and hydrogen abbreviation are enabled, hydrogen-2 and hydrogen-3 are written as D and T.

Rotatable-Bond Modes

calc_num_rotatable_bonds() accepts mode="default", "non_strict", "strict", or "strict_linkages". Unknown modes raise ValueError.