[Python-checkins] cpython (2.7): Document another recipe for itertools: all_equal(). Inspired by David Beazley.

[raymond.hettinger]

https://hg.python.org/cpython/rev/82add23abc54
changeset:   100436:82add23abc54
branch:      2.7
parent:      100432:d135799e952b
user:        Raymond Hettinger <python at rcn.com>
date:        Sun Mar 06 18:06:29 2016 -0800
summary:
  Document another recipe for itertools:  all_equal().  Inspired by David Beazley.

files:
  Doc/library/itertools.rst  |  5 +++++
  Lib/test/test_itertools.py |  8 ++++++++
  2 files changed, 13 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
@@ -695,6 +695,11 @@
        "Returns the nth item or a default value"
        return next(islice(iterable, n, None), default)
 
+   def all_equal(iterable):
+       "Returns True if all the elements are equal to each other"
+       g = groupby(iterable)
+       return next(g, True) and not next(g, False)
+
    def quantify(iterable, pred=bool):
        "Count how many times the predicate is true"
        return sum(imap(pred, iterable))
diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -1525,6 +1525,11 @@
 ...     "Returns the nth item or a default value"
 ...     return next(islice(iterable, n, None), default)
 
+>>> def all_equal(iterable):
+...     "Returns True if all the elements are equal to each other"
+...     g = groupby(iterable)
+...     return next(g, True) and not next(g, False)
+
 >>> def quantify(iterable, pred=bool):
 ...     "Count how many times the predicate is true"
 ...     return sum(imap(pred, iterable))
@@ -1623,6 +1628,9 @@
 >>> nth('abcde', 9) is None
 True
 
+>>> [all_equal(s) for s in ('', 'A', 'AAAA', 'AAAB', 'AAABA')]
+[True, True, True, False, False]
+
 >>> quantify(xrange(99), lambda x: x%2==0)
 50
 

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