Make python binding sample work without numpy installed.

Author: syoyo

python/sample.py

@@ -1,6 +1,13 @@
 import sys
 import tinyobjloader
 
+is_numpy_available = False
+try:
+  import numpy
+  is_numpy_available = True
+except:
+  print("NumPy not installed. Do not use numpy_*** API. If you encounter slow performance, see a performance tips for non-numpy API https://github.com/tinyobjloader/tinyobjloader/issues/275")
+
 filename = "../models/cornell_box.obj"
 
 
@@ -24,9 +31,9 @@
     print("Warn:", reader.Warning())
 
 attrib = reader.GetAttrib()
-print("attrib.vertices = ", len(attrib.vertices))
-print("attrib.normals = ", len(attrib.normals))
-print("attrib.texcoords = ", len(attrib.texcoords))
+print("len(attrib.vertices) = ", len(attrib.vertices))
+print("len(attrib.normals) = ", len(attrib.normals))
+print("len(attrib.texcoords) = ", len(attrib.texcoords))
 
 # vertex data must be `xyzxyzxyz...`
 assert len(attrib.vertices) % 3 == 0
@@ -37,6 +44,19 @@
 # texcoords data must be `uvuvuv...`
 assert len(attrib.texcoords) % 2 == 0
 
+# Performance note
+# (direct?) array access through member variable is quite slow.
+# https://github.com/tinyobjloader/tinyobjloader/issues/275#issuecomment-753465833
+# 
+# We encourage first copy(?) varible to Python world:
+#
+# vertices = attrib.vertices
+#
+# for i in range(...)
+#   v = vertices[i]
+#
+# Or please consider using numpy_*** interface(e.g. numpy_vertices())
+
 for (i, v) in enumerate(attrib.vertices):
     print("v[{}] = {}".format(i, v))
 
@@ -46,7 +66,10 @@
 for (i, v) in enumerate(attrib.texcoords):
     print("vt[{}] = {}".format(i, t))
 
-print("numpy_vertices = {}".format(attrib.numpy_vertices()))
+if is_numpy_available:
+    print("numpy_v = {}".format(attrib.numpy_vertices()))
+    print("numpy_vn = {}".format(attrib.numpy_normals()))
+    print("numpy_vt = {}".format(attrib.numpy_texcoords()))
 
 materials = reader.GetMaterials()
 print("Num materials: ", len(materials))
@@ -73,6 +96,9 @@
         print("[{}] v_idx {}".format(i, idx.vertex_index))
         print("[{}] vn_idx {}".format(i, idx.normal_index))
         print("[{}] vt_idx {}".format(i, idx.texcoord_index))
-    print("numpy_indices = {}".format(shape.mesh.numpy_indices()))
-    print("numpy_num_face_vertices = {}".format(shape.mesh.numpy_num_face_vertices()))
-    print("numpy_material_ids = {}".format(shape.mesh.numpy_material_ids()))
+    print("material_ids = {}".format(shape.mesh.material_ids))
+
+    if is_numpy_available:
+        print("numpy_indices = {}".format(shape.mesh.numpy_indices()))
+        print("numpy_num_face_vertices = {}".format(shape.mesh.numpy_num_face_vertices()))
+        print("numpy_material_ids = {}".format(shape.mesh.numpy_material_ids()))