diff --git a/.ipynb_checkpoints/palindrome_timeit-checkpoint.ipynb b/.ipynb_checkpoints/palindrome_timeit-checkpoint.ipynb
index a52018b..ef0e33f 100644
--- a/.ipynb_checkpoints/palindrome_timeit-checkpoint.ipynb
+++ b/.ipynb_checkpoints/palindrome_timeit-checkpoint.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:2d59017b21afaeadb093fa062632884c6d9d2e32933483326066a3219fba638c"
+  "signature": "sha256:6ea19109869c82ee989c8ea0599ec49401e74246a542ad0b7b05f6ef464bda19"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -45,6 +45,11 @@
       "    letters = [c for c in my_str.lower() if c in LOWERS]\n",
       "    return letters == letters[::-1]\n",
       "\n",
+      "LOWERS = set(string.ascii_lowercase)\n",
+      "def palindrome_stringlib2(my_str):\n",
+      "    letters = [c for c in my_str.lower() if c in LOWERS]\n",
+      "    return letters == letters[::-1]\n",
+      "\n",
       "def palindrome_isalpha(my_str):\n",
       "    stripped_str = [l for l in my_str.lower() if l.isalpha()]\n",
       "    return stripped_str == stripped_str[::-1]\n",
@@ -74,7 +79,7 @@
      "language": "python",
      "metadata": {},
      "outputs": [],
-     "prompt_number": 7
+     "prompt_number": 10
     },
     {
      "cell_type": "code",
@@ -86,6 +91,7 @@
       "%timeit palindrome_short(test_str)\n",
       "%timeit palindrome_regex(test_str)\n",
       "%timeit palindrome_stringlib(test_str)\n",
+      "%timeit palindrome_stringlib2(test_str)\n",
       "%timeit palindrome_isalpha(test_str)\n",
       "\n",
       "print('\\n\\nfunctions considering all characters (case-sensitive)')\n",
@@ -109,7 +115,7 @@
        "stream": "stdout",
        "text": [
         "\n",
-        "10000 loops, best of 3: 20.2 \u00b5s per loop"
+        "100000 loops, best of 3: 19.9 \u00b5s per loop"
        ]
       },
       {
@@ -117,7 +123,7 @@
        "stream": "stdout",
        "text": [
         "\n",
-        "100000 loops, best of 3: 12 \u00b5s per loop"
+        "100000 loops, best of 3: 13.5 \u00b5s per loop"
        ]
       },
       {
@@ -125,7 +131,15 @@
        "stream": "stdout",
        "text": [
         "\n",
-        "100000 loops, best of 3: 9.45 \u00b5s per loop"
+        "100000 loops, best of 3: 8.58 \u00b5s per loop"
+       ]
+      },
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "\n",
+        "100000 loops, best of 3: 9.42 \u00b5s per loop"
        ]
       },
       {
@@ -136,7 +150,7 @@
         "\n",
         "\n",
         "functions considering all characters (case-sensitive)\n",
-        "1000000 loops, best of 3: 498 ns per loop"
+        "1000000 loops, best of 3: 508 ns per loop"
        ]
       },
       {
@@ -144,7 +158,7 @@
        "stream": "stdout",
        "text": [
         "\n",
-        "100000 loops, best of 3: 3.28 \u00b5s per loop"
+        "100000 loops, best of 3: 3.08 \u00b5s per loop"
        ]
       },
       {
@@ -152,7 +166,7 @@
        "stream": "stdout",
        "text": [
         "\n",
-        "1000000 loops, best of 3: 478 ns per loop"
+        "1000000 loops, best of 3: 480 ns per loop"
        ]
       },
       {
@@ -163,7 +177,7 @@
        ]
       }
      ],
-     "prompt_number": 8
+     "prompt_number": 11
     },
     {
      "cell_type": "code",