Merge heads
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 3020128..8b7eef5 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -498,11 +498,14 @@
of the *value* argument, however there is a standard formatting syntax that
is used by most built-in types: :ref:`formatspec`.
- .. note::
+ The default *format_spec* is an empty string which usually gives the same
+ effect as calling ``str(value)``.
- ``format(value, format_spec)`` merely calls
- ``value.__format__(format_spec)``.
-
+ A call to ``format(value, format_spec)`` is translated to
+ ``type(value).__format__(format_spec)`` which bypasses the instance
+ dictionary when searching for the value's :meth:`__format__` method. A
+ :exc:`TypeError` exception is raised if the method is not found or if either
+ the *format_spec* or the return value are not strings.
.. function:: frozenset([iterable])
:noindex: