[Python-checkins] cpython (3.3): Closes #18646: improve lambda docs in tutorial. Original patch by Terry Reedy.

[georg.brandl]

http://hg.python.org/cpython/rev/ef1a17d5e263
changeset:   86022:ef1a17d5e263
branch:      3.3
parent:      86018:9cd4d650d08b
user:        Georg Brandl <georg at python.org>
date:        Sun Oct 06 10:22:45 2013 +0200
summary:
  Closes #18646: improve lambda docs in tutorial.  Original patch by Terry Reedy.

files:
  Doc/tutorial/controlflow.rst |  27 +++++++++++++++--------
  1 files changed, 17 insertions(+), 10 deletions(-)


diff --git a/Doc/tutorial/controlflow.rst b/Doc/tutorial/controlflow.rst
--- a/Doc/tutorial/controlflow.rst
+++ b/Doc/tutorial/controlflow.rst
@@ -583,17 +583,16 @@
 
 .. _tut-lambda:
 
-Lambda Forms
-------------
+Lambda Expressions
+------------------
 
-By popular demand, a few features commonly found in functional programming
-languages like Lisp have been added to Python.  With the :keyword:`lambda`
-keyword, small anonymous functions can be created. Here's a function that
-returns the sum of its two arguments: ``lambda a, b: a+b``.  Lambda forms can be
-used wherever function objects are required.  They are syntactically restricted
-to a single expression.  Semantically, they are just syntactic sugar for a
-normal function definition.  Like nested function definitions, lambda forms can
-reference variables from the containing scope::
+Small anonymous functions can be created with the :keyword:`lambda` keyword.
+This function returns the sum of its two arguments: ``lambda a, b: a+b``.
+Lambda forms can be used wherever function objects are required.  They are
+syntactically restricted to a single expression.  Semantically, they are just
+syntactic sugar for a normal function definition.  Like nested function
+definitions, lambda functions can reference variables from the containing
+scope::
 
    >>> def make_incrementor(n):
    ...     return lambda x: x + n
@@ -604,6 +603,14 @@
    >>> f(1)
    43
 
+The above example uses a lambda expression to return a function.  Another use
+is to pass a small function as an argument::
+
+   >>> pairs = [(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')]
+   >>> pairs.sort(key=lambda pair: pair[1])
+   >>> pairs
+   [(4, 'four'), (1, 'one'), (3, 'three'), (2, 'two')]
+
 
 .. _tut-docstrings:
 

-- 
Repository URL: http://hg.python.org/cpython