Generating InChI's Mini-Me, the InChIKey

A recent comment about Pybel's inability to calculate the InChIKey lead me to investigate. It's true enough that currently the InChIKey is not one of the available formats in Pybel. However, by accessing OpenBabel directly it's possible to generate InChIkeys. Here's how.

The InChIKey is available as an option on the InChI format. How would you find this out? Well, "babel -Hinchi" gives all of the options, one of which is option "K" indicating "output InChIKey". Here's how to do a SMILES to InChIKey conversion from Python:

import openbabel as ob

conv = ob.OBConversion()
conv.SetInAndOutFormats("smi", "inchi")
conv.SetOptions("K", conv.OUTOPTIONS)

mol = ob.OBMol()
conv.ReadString(mol, "CC(=O)Cl")
inchikey = conv.WriteString(mol)
assert inchikey == "WETWJCDKMRHUPV-UHFFFAOYAQ"

A future version of Pybel will include the InChIKey format directly.

Image credit: Gustty