From 353c380762f6855d38648ede5100ac453ebca468 Mon Sep 17 00:00:00 2001
From: immerrr <immerrr@gmail.com>
Date: Fri, 3 Jun 2016 20:37:40 +0300
Subject: [PATCH] iterutils: optimize chunked_iter

---
 boltons/iterutils.py | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/boltons/iterutils.py b/boltons/iterutils.py
index 6cc5eb5..3037896 100644
--- a/boltons/iterutils.py
+++ b/boltons/iterutils.py
@@ -218,17 +218,13 @@ def chunked_iter(src, size, **kw):
     postprocess = lambda chk: chk
     if isinstance(src, basestring):
         postprocess = lambda chk, _sep=type(src)(): _sep.join(chk)
-    cur_chunk = []
-    i = 0
-    for item in src:
-        cur_chunk.append(item)
-        i += 1
-        if i % size == 0:
-            yield postprocess(cur_chunk)
-            cur_chunk = []
-    if cur_chunk:
-        if do_fill:
-            lc = len(cur_chunk)
+    src_iter = iter(src)
+    while True:
+        cur_chunk = list(itertools.islice(src_iter, size))
+        if not cur_chunk:
+            break
+        lc = len(cur_chunk)
+        if lc < size and do_fill:
             cur_chunk[lc:] = [fill_val] * (size - lc)
         yield postprocess(cur_chunk)
     return