sdk/platform-tools/systrace/catapult/telemetry/telemetry/internal/util/classes.py

   1 # Copyright 2014 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 import inspect
   6
   7
   8 def IsDirectlyConstructable(cls):
   9   """Returns True if instance of |cls| can be construct without arguments."""
  10   assert inspect.isclass(cls)
  11   if not hasattr(cls, '__init__'):
  12     # Case |class A: pass|.
  13     return True
  14   if cls.__init__ is object.__init__:
  15     # Case |class A(object): pass|.
  16     return True
  17   # Case |class (object):| with |__init__| other than |object.__init__|.
  18   args, _, _, defaults = inspect.getargspec(cls.__init__)
  19   if defaults is None:
  20     defaults = ()
  21   # Return true if |self| is only arg without a default.
  22   return len(args) == len(defaults) + 1