Fix filter_out: nan filer (#486)

* Fix filter_out nan filter

Fixes https://github.com/esphome/issues/issues/138

* Add test

esphome/cpp_generator.py

@@ -1,4 +1,5 @@
 from collections import OrderedDict
+import math
 
 from esphome.core import CORE, HexInt, Lambda, TimePeriod, TimePeriodMicroseconds, \
     TimePeriodMilliseconds, TimePeriodSeconds, TimePeriodMinutes
@@ -260,6 +261,8 @@ class FloatLiteral(Literal):
         self.float_ = value
 
     def __str__(self):
+        if math.isnan(self.float_):
+            return u"NAN"
         return u"{:f}f".format(self.float_)
 
 

tests/test1.yaml

@@ -173,6 +173,7 @@ sensor:
         - 40.0 -> 45.0
         - 100.0 -> 102.5
       - filter_out: 42.0
+      - filter_out: nan
       - sliding_window_moving_average:
           window_size: 15
           send_every: 15