From: Raymond Hettinger <python@rcn.com>
Date: Mon, 7 Mar 2016 02:06:29 +0000 (-0800)
Subject: Document another recipe for itertools:  all_equal().  Inspired by David Beazley.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2ec5fd546f5fb98f84e3910301d53cfa30add15d;p=python

Document another recipe for itertools:  all_equal().  Inspired by David Beazley.
---

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index ea279b0125..a48f69274a 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -695,6 +695,11 @@ which incur interpreter overhead.
        "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
index 753aa17afa..8b5f051f18 100644
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -1525,6 +1525,11 @@ Samuele
 ...     "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 @@ perform as purported.
 >>> 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