Issue #27934: Use float.__repr__ instead of plain repr when JSON-encoding an instance of a float subclass. Thanks Eddie James.
diff --git a/Lib/json/encoder.py b/Lib/json/encoder.py
index f5eeed7..97ffe8e 100644
--- a/Lib/json/encoder.py
+++ b/Lib/json/encoder.py
@@ -28,7 +28,7 @@
     #ESCAPE_DCT.setdefault(chr(i), '\\u%04x' % (i,))
 
 INFINITY = float('inf')
-FLOAT_REPR = repr
+FLOAT_REPR = float.__repr__
 
 def encode_basestring(s):
     """Return a JSON representation of a Python string