Combine .ITP files from gromacs into 'combo.itp' file

combine_ITP.py

def read_itp(itp_name):
    lines = open(itp_name).readlines()
    impDat = []
    for n in  range(len(lines)): 
        if '[' in lines[n]: impDat.append(n)
    atom_def = lines[impDat[0]+1:impDat[1]] 
    rest_mol = lines[impDat[1]:]
    return(atom_def,rest_mol) 
a_UNK,r_UNK=read_itp('UNK.itp')
a_OCT,r_OCT=read_itp('OCT.itp')
a_CYH,r_CYH=read_itp('CYH.itp')

atypes   = list(set(a_UNK +a_OCT + a_CYH)) 
moltypes = r_UNK + r_OCT + r_CYH
ofile=open('combo.itp','w')
ofile.write('[ atomtypes ] \n')
for line in atypes: ofile.write('%s'%line)
for line in moltypes: ofile.write('%s'%line)
ofile.close()
print('-maxwarn %d'%(len(a_CYH+a_OCT)))