classify abs() argument type (GH-8103)

diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index f5427a4072a802c97c0954187630beef4a432f88..6476cbd65e01512a518faa0d55c545da0036edfa 100644 (file)
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -44,7 +44,8 @@ are always available.  They are listed here in alphabetical order.
 
    Return the absolute value of a number.  The argument may be an
    integer or a floating point number.  If the argument is a complex number, its
-   magnitude is returned.
+   magnitude is returned. If *x* defines :meth:`__abs__`,
+   ``abs(x)`` returns ``x.__abs__()``.
 
 
 .. function:: all(iterable)