Adding new built-in function sum, with docs and tests.

2 files changed, 12 insertions, 1 deletions

diff --git a/Doc/lib/libfuncs.tex b/Doc/lib/libfuncs.tex
index 323a516..50f22f8 100644
--- a/Doc/lib/libfuncs.tex
+++ b/Doc/lib/libfuncs.tex
@@ -897,6 +897,14 @@ class C:
   \versionadded{2.2}
 \end{funcdesc}
 
+\begin{funcdesc}{sum}{sequence\optional{start=0}}
+  Sums up the items of a \var{sequence}, from left to right, and returns
+  the total.  The \var{sequence}'s items are normally numbers, and are
+  not allowed to be strings.  The fast, correct way to join up a
+  sequence of strings is by calling \code{''.join(\var{sequence})}.
+  \versionadded{2.3}
+\end{funcdesc}
+
 \begin{funcdesc}{super}{type\optional{object-or-type}}
   Return the superclass of \var{type}.  If the second argument is omitted
   the super object returned is unbound.  If the second argument is an
diff --git a/Doc/tut/tut.tex b/Doc/tut/tut.tex
index 71d3f60..b227576 100644
--- a/Doc/tut/tut.tex
+++ b/Doc/tut/tut.tex
@@ -1819,6 +1819,9 @@ item, then to the result and the next item, and so on.  For example,
 0
 \end{verbatim}
 
+Don't use this example's definition of \code{sum}: since summing numbers
+is such a common need, a built-in function \code{sum(\var{sequence})} is 
+already provided, and works exactly like this\versionadded{2,3}.
 
 \subsection{List Comprehensions}
 
@@ -2502,7 +2505,7 @@ standard module \module{__builtin__}\refbimodindex{__builtin__}:
  'len', 'license', 'list', 'locals', 'long', 'map', 'max', 'min',
  'object', 'oct', 'open', 'ord', 'pow', 'property', 'quit',
  'range', 'raw_input', 'reduce', 'reload', 'repr', 'round',
- 'setattr', 'slice', 'staticmethod', 'str', 'string', 'super',
+ 'setattr', 'slice', 'staticmethod', 'str', 'string', 'sum', 'super',
  'tuple', 'type', 'unichr', 'unicode', 'vars', 'xrange', 'zip']
 \end{verbatim}