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Changelog

1.5.1 (2025-11-01)

New Features

  • Add + operator to combine two ChemFormula instances by summing element counts and charges (see example6.py)
  • Add - operator to subtract one ChemFormula instance from another one by subtracting element counts and charges (see example6.py)
  • Add * operator to multiply element counts and charge with a positive integer from left and right

Example

from chemformula import ChemFormula

water = ChemFormula("H2O")
proton = ChemFormula("H", 1)

oxonium = water + proton  # => ChemFormula("H3O", 1)
hydroxonium = oxonium + 3 * water  # => ChemFormula("H9O4", 1)

print(oxonium.hill_formula.unicode)  # => H₃O⁺
print(oxonium - proton == water)  # True
print(hydroxonium.hill_formula.unicode)  # => H₉O₄⁺

1.5.0 (2025-09-14)

New Feature

  • Add support for hydrogen isotopes (deuterium "D" and tritium "T") via a global AllowHydrogenIsotopes flag in chemformula.config (see example5.py)
  • Implement .contains_isotopes attribute to the ChemFormula class for detecting specific isotopes in formulas

Deprecated Feature

  • Replace .radioactive property with .is_radioactive
  • .radioactive can still be used, but is flagged as deprecated and emits a DeprecationWarning

Example

import chemformula.config
from chemformula import ChemFormula

chemformula.config.AllowHydrogenIsotopes = True

heavy_water = ChemFormula("D2O")
print(f"{heavy_water.formula_weight:.2f} g/mol")  # => 20.03 g/mol

super_heavy_water = ChemFormula("T2O")
print(super_heavy_water.is_radioactive)  # => True