From ba9d148b4170e4080e09128de99426c49c74810f Mon Sep 17 00:00:00 2001
From: Ryan Grout <ryan@ryangrout.org>
Date: Wed, 5 Dec 2018 21:22:31 -0600
Subject: [PATCH 1/2] Use a non-recursive implementation inspired by cytoolz.

---
 toolz/dicttoolz.py | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/toolz/dicttoolz.py b/toolz/dicttoolz.py
index e07b35cd..84ba3a01 100644
--- a/toolz/dicttoolz.py
+++ b/toolz/dicttoolz.py
@@ -7,7 +7,6 @@
            'valfilter', 'keyfilter', 'itemfilter',
            'assoc', 'dissoc', 'assoc_in', 'update_in', 'get_in')
 
-
 def _get_factory(f, kwargs):
     factory = kwargs.pop('factory', dict)
     if kwargs:
@@ -266,16 +265,28 @@ def update_in(d, keys, func, default=None, factory=dict):
     >>> update_in({1: 'foo'}, [2, 3, 4], inc, 0)
     {1: 'foo', 2: {3: {4: 1}}}
     """
-    assert len(keys) > 0
-    k, ks = keys[0], keys[1:]
-    if ks:
-        return assoc(d, k, update_in(d[k] if (k in d) else factory(),
-                                     ks, func, default, factory),
-                     factory)
-    else:
-        innermost = func(d[k]) if (k in d) else func(default)
-        return assoc(d, k, innermost, factory)
+    ks = iter(keys)
+    k = next(ks)
+
+    rv = inner = factory()
+    rv.update(d)
+
+    for key in ks:
+        if k in d:
+            d = d[k]
+            dtemp = factory()
+            dtemp.update(d)
+        else:
+            d = dtemp = factory()
 
+        inner[k] = inner = dtemp
+        k = key
+
+    if k in d:
+        inner[k] = func(d[k])
+    else:
+        inner[k] = func(default)
+    return rv
 
 def get_in(keys, coll, default=None, no_default=False):
     """ Returns coll[i0][i1]...[iX] where [i0, i1, ..., iX]==keys.

From b2eb929e4c88c6876a8510e5229842556a001245 Mon Sep 17 00:00:00 2001
From: Ryan Grout <ryan@ryangrout.org>
Date: Wed, 5 Dec 2018 23:06:56 -0600
Subject: [PATCH 2/2] Fix linting error.

---
 toolz/dicttoolz.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/toolz/dicttoolz.py b/toolz/dicttoolz.py
index 84ba3a01..dbdd9eb7 100644
--- a/toolz/dicttoolz.py
+++ b/toolz/dicttoolz.py
@@ -7,6 +7,7 @@
            'valfilter', 'keyfilter', 'itemfilter',
            'assoc', 'dissoc', 'assoc_in', 'update_in', 'get_in')
 
+
 def _get_factory(f, kwargs):
     factory = kwargs.pop('factory', dict)
     if kwargs:
@@ -288,6 +289,7 @@ def update_in(d, keys, func, default=None, factory=dict):
         inner[k] = func(default)
     return rv
 
+
 def get_in(keys, coll, default=None, no_default=False):
     """ Returns coll[i0][i1]...[iX] where [i0, i1, ..., iX]==keys.