commit 8a72266eca00d31ae720453622728f72dd6b2694
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Sun Apr 08 14:37:30 2018 -0700
committer Raymond Hettinger <rhettinger@users.noreply.github.com> Sun Apr 08 14:37:30 2018 -0700
tree 106d357d05d23021eb5d18acc7e008a5144badc9
parent 31f1b52f1f6c2d84eacf3c6db3f6b9adf04b675e

Add a prepend() recipe to teach a chain() idiom (GH-6415) (GH-6421)

(cherry picked from commit 9265dd72e5ec1cfa5fcdb5be8ebffe1d9994bd4b)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>

Lib/test/test_itertools.py

diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
index effd7f0..cbbb4c4 100644
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -2198,6 +2198,11 @@
 ...     "Return first n items of the iterable as a list"
 ...     return list(islice(iterable, n))
 
+>>> def prepend(value, iterator):
+...     "Prepend a single value in front of an iterator"
+...     # prepend(1, [2, 3, 4]) -> 1 2 3 4
+...     return chain([value], iterator)
+
 >>> def enumerate(iterable, start=0):
 ...     return zip(count(start), iterable)
 
@@ -2350,6 +2355,9 @@
 >>> take(10, count())
 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
 
+>>> list(prepend(1, [2, 3, 4]))
+[1, 2, 3, 4]
+
 >>> list(enumerate('abc'))
 [(0, 'a'), (1, 'b'), (2, 'c')]