master: make is_stdlib_path() a free function

For Ansible module loader work.

mitogen/master.py

@@ -319,21 +319,19 @@ class LogForwarder(object):
         return 'LogForwarder(%r)' % (self._router,)
 
 
-class ModuleFinder(object):
 _STDLIB_PATHS = _stdlib_paths()
 
-    def __init__(self):
-        #: Import machinery is expensive, keep :py:meth`:get_module_source`
-        #: results around.
-        self._found_cache = {}
 
-        #: Avoid repeated dependency scanning, which is expensive.
-        self._related_cache = {}
+def is_stdlib_path(path):
+    return any(
+        os.path.commonprefix((libpath, path)) == libpath
+        and 'site-packages' not in path
+        and 'dist-packages' not in path
+        for libpath in _STDLIB_PATHS
+    )
 
-    def __repr__(self):
-        return 'ModuleFinder()'
 
-    def is_stdlib_name(self, modname):
+def is_stdlib_name(modname):
     """Return ``True`` if `modname` appears to come from the standard
     library."""
     if imp.is_builtin(modname) != 0:
@@ -345,14 +343,20 @@ class ModuleFinder(object):
 
     # six installs crap with no __file__
     modpath = os.path.abspath(getattr(module, '__file__', ''))
-        if 'site-packages' in modpath:
-            return False
+    return is_stdlib_path(modpath)
 
-        for dirname in self._STDLIB_PATHS:
-            if os.path.commonprefix((dirname, modpath)) == dirname:
-                return True
 
-        return False
+class ModuleFinder(object):
+    def __init__(self):
+        #: Import machinery is expensive, keep :py:meth`:get_module_source`
+        #: results around.
+        self._found_cache = {}
+
+        #: Avoid repeated dependency scanning, which is expensive.
+        self._related_cache = {}
+
+    def __repr__(self):
+        return 'ModuleFinder()'
 
     def _looks_like_script(self, path):
         """
@@ -515,7 +519,7 @@ class ModuleFinder(object):
                 name
                 for name in maybe_names
                 if sys.modules.get(name) is not None
-                and not self.is_stdlib_name(name)
+                and not is_stdlib_name(name)
                 and 'six.moves' not in name  # TODO: crap
             )
         ))