use a constant instead of a static factory method for duration.infinite

Signed-off-by: Emerson Knapp <eknapp@amazon.com>

rclpy/rclpy/duration.py

@@ -35,7 +35,7 @@ def __repr__(self):
  return 'Duration(nanoseconds={0})'.format(self.nanoseconds)
 
  def __str__(self):
- if self == Duration.Infinite():
+ if self == Infinite:
  return 'Infinite'
  return f'{self.nanoseconds} nanoseconds'
 
@@ -82,9 +82,9 @@ def from_msg(cls, msg):
  raise TypeError('Must pass a builtin_interfaces.msg.Duration object')
  return cls(seconds=msg.sec, nanoseconds=msg.nanosec)
 
- @classmethod
- def Infinite(cls):
- return cls(nanoseconds=_rclpy.RMW_DURATION_INFINITE)
-
  def get_c_duration(self):
  return self._duration_handle
+
+
+# Constant representing an infinite amount of time.
+Infinite = Duration(nanoseconds=_rclpy.RMW_DURATION_INFINITE)

rclpy/test/test_time.py

@@ -16,6 +16,7 @@
 
 from rclpy.clock import ClockType
 from rclpy.duration import Duration
+from rclpy.duration import Infinite
 from rclpy.time import Time
 
 from test_msgs.msg import Builtins
@@ -230,5 +231,5 @@ def test_seconds_nanoseconds(self):
  assert (0, 0) == Time().seconds_nanoseconds()
 
  def test_infinite_duration(self):
- duration = Duration.Infinite()
+ duration = Infinite
  assert str(duration) == 'Infinite'