diff -r 4d00d0109147 Lib/string.py
--- a/Lib/string.py	Wed Jan 07 00:37:01 2015 +1000
+++ b/Lib/string.py	Wed Jan 07 00:03:11 2015 +0100
@@ -29,6 +29,21 @@
 
 # Functions which aren't available as string methods.
 
+
+def from_iterable(iterable, map_function=None):
+    """from_iterable(iterable [,map_function]) -> string
+
+    Create a string from the given iterable. The map_function argument specify
+    a one-argument mapping function that will be applied to each element of the
+    iterable. In any way the str() constructor will be applied to each element,
+    after the transformation.
+
+    """
+    if map_function is None:
+        map_function = lambda x: x
+    return "".join(str(map_function(el)) for el in iterable)
+
+
 # Capitalize the words in a string, e.g. " aBc  dEf " -> "Abc Def".
 def capwords(s, sep=None):
     """capwords(s [,sep]) -> string