From 4ea6619556e02f218fa9b4c893d2d2aa41479c69 Mon Sep 17 00:00:00 2001
From: Ryan Grout <ryan@ryangrout.org>
Date: Thu, 9 Aug 2018 21:43:53 -0500
Subject: [PATCH 1/3] Avoid overhead of islice.

---
 toolz/itertoolz.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/toolz/itertoolz.py b/toolz/itertoolz.py
index 71c7ddc0..bf91903f 100644
--- a/toolz/itertoolz.py
+++ b/toolz/itertoolz.py
@@ -374,7 +374,9 @@ def second(seq):
     >>> second('ABC')
     'B'
     """
-    return next(itertools.islice(seq, 1, None))
+    seq = iter(seq)
+    next(seq)
+    return next(seq)
 
 
 def nth(n, seq):

From 701712f8947aa845b01eb90505104885dbc95a26 Mon Sep 17 00:00:00 2001
From: Ryan Grout <ryan@ryangrout.org>
Date: Tue, 14 Aug 2018 21:44:59 -0500
Subject: [PATCH 2/3] Handle StopIteration in Python 3.7+

Add more tests for edge cases
---
 toolz/itertoolz.py            | 7 +++++--
 toolz/tests/test_itertoolz.py | 8 ++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/toolz/itertoolz.py b/toolz/itertoolz.py
index bf91903f..b8028c49 100644
--- a/toolz/itertoolz.py
+++ b/toolz/itertoolz.py
@@ -375,8 +375,11 @@ def second(seq):
     'B'
     """
     seq = iter(seq)
-    next(seq)
-    return next(seq)
+    try:
+        next(seq)
+        return next(seq)
+    except StopIteration:
+        raise
 
 
 def nth(n, seq):
diff --git a/toolz/tests/test_itertoolz.py b/toolz/tests/test_itertoolz.py
index e0a8d17f..bd83db2f 100644
--- a/toolz/tests/test_itertoolz.py
+++ b/toolz/tests/test_itertoolz.py
@@ -17,6 +17,8 @@
 from toolz.compatibility import range, filter
 from operator import add, mul
 
+import pytest
+
 
 # is comparison will fail between this and no_default
 no_default2 = loads(dumps('__no__default__'))
@@ -143,6 +145,12 @@ def test_second():
     assert second('ABCDE') == 'B'
     assert second((3, 2, 1)) == 2
     assert isinstance(second({0: 'zero', 1: 'one'}), int)
+    assert second(x for x in range(2)) == 1
+
+    # Python 3.7, StopIteration should be raised if iterable too short
+    with pytest.raises(StopIteration):
+        second([])
+        second([0])
 
 
 def test_last():

From 307b0bbdc1d7247b9d86ea3abf5b1f89648b9f60 Mon Sep 17 00:00:00 2001
From: Ryan Grout <ryan@ryangrout.org>
Date: Tue, 14 Aug 2018 22:14:54 -0500
Subject: [PATCH 3/3] Revert "Handle StopIteration in Python 3.7+"

This reverts commit 701712f8947aa845b01eb90505104885dbc95a26.
---
 toolz/itertoolz.py            | 7 ++-----
 toolz/tests/test_itertoolz.py | 8 --------
 2 files changed, 2 insertions(+), 13 deletions(-)

diff --git a/toolz/itertoolz.py b/toolz/itertoolz.py
index b8028c49..bf91903f 100644
--- a/toolz/itertoolz.py
+++ b/toolz/itertoolz.py
@@ -375,11 +375,8 @@ def second(seq):
     'B'
     """
     seq = iter(seq)
-    try:
-        next(seq)
-        return next(seq)
-    except StopIteration:
-        raise
+    next(seq)
+    return next(seq)
 
 
 def nth(n, seq):
diff --git a/toolz/tests/test_itertoolz.py b/toolz/tests/test_itertoolz.py
index bd83db2f..e0a8d17f 100644
--- a/toolz/tests/test_itertoolz.py
+++ b/toolz/tests/test_itertoolz.py
@@ -17,8 +17,6 @@
 from toolz.compatibility import range, filter
 from operator import add, mul
 
-import pytest
-
 
 # is comparison will fail between this and no_default
 no_default2 = loads(dumps('__no__default__'))
@@ -145,12 +143,6 @@ def test_second():
     assert second('ABCDE') == 'B'
     assert second((3, 2, 1)) == 2
     assert isinstance(second({0: 'zero', 1: 'one'}), int)
-    assert second(x for x in range(2)) == 1
-
-    # Python 3.7, StopIteration should be raised if iterable too short
-    with pytest.raises(StopIteration):
-        second([])
-        second([0])
 
 
 def test_last():