Define execfile, file, long, raw_input, xrange for Python 3

samples/python/_doc.py

@@ -7,8 +7,6 @@ ones with missing __doc__ string.
 
 # Python 2/3 compatibility
 from __future__ import print_function
-import sys
-PY3 = sys.version_info[0] == 3
 
 from glob import glob
 
@@ -17,11 +15,11 @@ if __name__ == '__main__':
     for fn in glob('*.py'):
         loc = {}
         try:
-            if PY3:
-                exec(open(fn).read(), loc)
-            else:
-                execfile(fn, loc)
-        except:
+            try:
+                execfile(fn, loc)           # Python 2
+            except NameError:
+                exec(open(fn).read(), loc)  # Python 3
+        except Exception:
             pass
         if '__doc__' not in loc:
             print(fn)