SMILES atom regex.ipynb

SMILES atom regex.ipynb

This regex doesn't handle * terms, and it interprets 'Cc' as a single atom term, rather than the two atoms terms 'C' and 'c'.

Here's an alternative version which handles both these cases, written using re's "verbose" notation:

atom_finder = re.compile(r"""
(
 Cl? |             # Cl and Br are part of the organic subset
 Br? |
 [NOSPFIbcnosp*] | # as are these single-letter elements
 \[[^]]+\]         # everything else must be in []s
)
""", re.X)

Thanks Andrew!