Add Tim Peters' shuffle() algorithm.
diff --git a/Lib/random.py b/Lib/random.py
index 9ec41e1..9e899ad 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -292,6 +292,27 @@
u = random()
return alpha * pow(-log(u), 1.0/beta)
+# -------------------- shuffle --------------------
+# Not quite a random distribution, but a standard algorithm.
+# This implementation due to Tim Peters.
+
+def shuffle(x, random=random, int=int):
+ """x, random=random.random -> shuffle list x in place; return None.
+
+ Optional arg random is a 0-argument function returning a random
+ float in [0.0, 1.0); by default, the standard random.random.
+
+ Note that for even rather small len(x), the total number of
+ permutations of x is larger than the period of most random number
+ generators; this implies that "most" permutations of a long
+ sequence can never be generated.
+ """
+
+ for i in xrange(len(x)-1, 0, -1):
+ # pick an element in x[:i+1] with which to exchange x[i]
+ j = int(random() * (i+1))
+ x[i], x[j] = x[j], x[i]
+
# -------------------- test program --------------------
def test(N = 200):