openmesh_decimate.py

import openmesh as om
import numpy as np

mesh = om.read_trimesh('earth.obj', vertex_normal=True, vertex_tex_coord=True)

# make mesh handle these attributes
mesh.request_vertex_normals()
mesh.request_vertex_texcoords2D()

# create decimater
decimator = om.TriMeshDecimater(mesh)

# Quadric decimater module (there's other modules as well..)
# print dir(om)
modQ = om.TriMeshModQuadricHandle()

# add it to the decimater
decimator.add(modQ)

# setup Quadric module
decimator.module(modQ).set_max_err(1e-5)
decimator.module(modQ).set_binary(False)

# initialize
decimator.initialize()

# go!
decimator.decimate_to(int(len(mesh.points()) * 0.1))

# always needed after decimation
mesh.garbage_collection()

om.write_mesh('test.obj', mesh, vertex_normal=True, vertex_tex_coord=True)

I just found it didn't work in my program and the model retained the same verts and faces.