Python script to convert *.ply to *.obj (3D formats)

ply2obj.py

'''
Simple script to convert ply to obj models
'''

from argparse import ArgumentParser
from plyfile import PlyData


def main():
    parser = ArgumentParser()
    parser.add_argument('ply_filename')
    parser.add_argument('obj_filename')

    args = parser.parse_args()

    convert(PlyData.read(args.ply_filename), args.obj_filename)

def convert(ply, obj):
    '''
    Convert given ply data
    '''

    with open(obj, 'w') as f:
        f.write("# OBJ file\n")

        verteces = ply['vertex']

        for v in verteces:
            p = [v['x'], v['y'], v['z']]
            c = [ v['red'] / 256 , v['green'] / 256 , v['blue'] / 256 ]
            a = p + c
            f.write("v %.6f %.6f %.6f %.6f %.6f %.6f \n" % tuple(a) )

        for v in verteces:
            n = [ v['nx'], v['ny'], v['nz'] ]
            f.write("vn %.6f %.6f %.6f\n" % tuple(n))

        for v in verteces:
            t = [ v['s'], v['t'] ]
            f.write("vt %.6f %.6f\n" % tuple(t))

        if 'face' in ply:
            for i in ply['face']['vertex_indices']:
                f.write("f")
                for j in range(i.size):
                    # ii = [ i[j]+1 ]
                    ii = [ i[j]+1, i[j]+1, i[j]+1 ]
                    # f.write(" %d" % tuple(ii) )
                    f.write(" %d/%d/%d" % tuple(ii) )
                f.write("\n")

main()

It could be PLY file's wrong format but the script writes 21 thousand lines to OBJ file and then breaks with the following error:

Traceback (most recent call last):
  File "ply2obj.py", line 52, in <module>
    main()
  File "ply2obj.py", line 16, in main
    convert(PlyData.read(args.ply_filename), args.obj_filename)
  File "ply2obj.py", line 35, in convert
    n = [ v['nx'], v['ny'], v['nz'] ]
ValueError: no field of name nx

Doesn't work. RealSense output file PLY would not convert.
Traceback (most recent call last):
File "D:\projects\AR\PLYtoOBJ.py", line 52, in
main()
File "D:\projects\AR\PLYtoOBJ.py", line 16, in main
convert(PlyData.read(args.ply_filename), args.obj_filename)
File "D:\projects\AR\PLYtoOBJ.py", line 35, in convert
n = [ v['nx'], v['ny'], v['nz'] ]
ValueError: no field of name nx

Must be some field not yet accounted for.
Thanks though for helping me get this far.

I had the same issue. This is hapenning if your .ply is missing some attributes (which are mandatory in this script).

I fixed these fields to be optional. You may update your gist:
ply_to_obj.py

Anyone looking for this might also be interested in https://github.com/nschloe/meshio