def get_CA_or(res: Residue) -> Atom:
"""Returns the alpha carbon for the resiude if there is one, else the first atom in the list"""
atoms: List[Atom] = list(res.get_atoms())
alphacarbons = list(
filter(lambda atom: True if atom.get_name() == 'CA' else False, atoms))
return atoms[0] if len(alphacarbons) == 0 else alphacarbons[0]
def get_alpha_carbon(res:Residue)->Atom:
"""Get the first(only) alpha carbon in the residue or an exception"""
alpha_carbons: List[Atom] = list( filter(lambda internal_atom: internal_atom.get_id() =='CA', res.get_atoms()) )
if len(alpha_carbons) != 1:
raise Exception(f"Alpha carbon not found or duplicated in residue {res.get_full_id()}")
return alpha_carbons[0]
