run.single() to run a propka calculation without script

- can pass a single pdffile (or stream(!))
- added options lib.loadOptions() to pass opt string

propka/run.py

@@ -13,3 +13,21 @@ def main():
         my_molecule = propka.molecular_container.Molecular_container(pdbfile, options)
         my_molecule.calculate_pka()
         my_molecule.write_pka()
+
+def single(pdbfile, optargs=None):
+    """Run a single PROPKA calculation using *pdbfile* as input.
+
+    Commandline options can be passed as a **list** in *optargs*.
+
+    .. rubric:: Example
+
+    ::
+       single("protein.pdb", optargs=["--mutation=N25R/N181D", "-v", "--pH=7.2"])
+    """
+    optargs = optargs if optargs is not None else []
+    options, ignored_pdbfiles = propka.lib.loadOptions(*optargs)
+
+    my_molecule = propka.molecular_container.Molecular_container(pdbfile, options)
+    my_molecule.calculate_pka()
+    my_molecule.write_pka()
+    return my_molecule