Issue #5920: Changed format.__float__ and complex.__float__ to use a precision of 12 when using the empty presentation type. This more closely matches str()'s behavior and reduces surprises when adding alignment flags to an empty format string. Patch by Mark Dickinson.
diff --git a/Misc/NEWS b/Misc/NEWS
index 26af9bb..d6c6227 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,15 @@
Core and Builtins
-----------------
+- Issue #5920: For float.__format__, change the behavior with the
+ empty presentation type (that is, not one of 'e', 'f', 'g', or 'n')
+ to be like 'g' but with at least one decimal point and with a
+ default precision of 12. Previously, the behavior the same but with
+ a default precision of 6. This more closely matches str(), and
+ reduces surprises when adding alignment flags to the empty
+ presentation type. This also affects the new complex.__format__ in
+ the same way.
+
- Issue #5890: in subclasses of 'property' the __doc__ attribute was
shadowed by classtype's, even if it was None. property now
inserts the __doc__ into the subclass instance __dict__.