Printing protein amino acids histograms

A program that prints a histogram of the occurrences of various amino acids in a protein. An example command would be:

prompt> python reshist.py input.pdb

Code

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reshist.py

#!/usr/bin/env python
# (C) 2022 Cadence Design Systems, Inc. (Cadence) 
# All rights reserved.
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#############################################################################
# Print a histogram of the occurrences of various amino acids in a protein
#############################################################################
import sys
from openeye import oechem


def ResHist(ifs):
    nrmol = 0
    mol = oechem.OEGraphMol()
    while oechem.OEReadMolecule(ifs, mol):
        nrmol += 1
        print("==============================")
        print("Molecule: %d Title: %s" % (nrmol, mol.GetTitle()))

        nrres = 0
        resmap = {}
        if not oechem.OEHasResidues(mol):
            oechem.OEPerceiveResidues(mol, oechem.OEPreserveResInfo_All)
        hv = oechem.OEHierView(mol)
        for res in hv.GetResidues():
            nrres += 1
            name = res.GetOEResidue().GetName()
            if name in resmap:
                resmap[name] += 1
            else:
                resmap[name] = 1

    sortedres = sorted(resmap.keys())
    for name in sortedres:
        percent = 100.0*float(resmap[name])/float(nrres)
        print("%3s %3d  %4.1f %%" % (name, resmap[name], percent))


if __name__ == "__main__":
    if len(sys.argv) != 2:
        oechem.OEThrow.Usage("reshist.py <infile>")
    ifs = oechem.oemolistream()
    if not ifs.open(sys.argv[1]):
        oechem.OEThrow.Fatal("Unable to open %s for reading" % sys.argv[1])
    ResHist(ifs)