[Python-checkins] cpython (2.7): Add an itertools recipe showing how to use t.__copy__().

[raymond.hettinger]

http://hg.python.org/cpython/rev/1026b1d47f30
changeset:   83037:1026b1d47f30
branch:      2.7
parent:      83034:e044d22d2f61
user:        Raymond Hettinger <python at rcn.com>
date:        Sat Mar 30 23:37:57 2013 -0700
summary:
  Add an itertools recipe showing how to use t.__copy__().

files:
  Doc/library/itertools.rst |  12 ++++++++++++
  1 files changed, 12 insertions(+), 0 deletions(-)


diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -828,6 +828,18 @@
        indices = sorted(random.randrange(n) for i in xrange(r))
        return tuple(pool[i] for i in indices)
 
+   def tee_lookahead(t, i):
+       """Inspect the i-th upcomping value from a tee object
+          while leaving the tee object at its current position.
+
+          Raise an IndexError if the underlying iterator doesn't
+          have enough values.
+
+       """
+       for value in islice(t.__copy__(), i, None):
+           return value
+       raise IndexError(i)
+
 Note, many of the above recipes can be optimized by replacing global lookups
 with local variables defined as default values.  For example, the
 *dotproduct* recipe can be written as::

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