diff --git a/Part.1.B.why.start.from.learning.coding.ipynb b/Part.1.B.why.start.from.learning.coding.ipynb
index ef3ba873d..a3d428f88 100644
--- a/Part.1.B.why.start.from.learning.coding.ipynb
+++ b/Part.1.B.why.start.from.learning.coding.ipynb
@@ -247,7 +247,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   }
  },
  "nbformat": 4,
diff --git a/Part.1.C.must.learn.sth.only.by.reading.ipynb b/Part.1.C.must.learn.sth.only.by.reading.ipynb
index f2e537e9c..3db68028d 100644
--- a/Part.1.C.must.learn.sth.only.by.reading.ipynb
+++ b/Part.1.C.must.learn.sth.only.by.reading.ipynb
@@ -124,7 +124,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   }
  },
  "nbformat": 4,
diff --git a/Part.1.D.preparation.for.reading.ipynb b/Part.1.D.preparation.for.reading.ipynb
index 23a871ebe..9a4565cc3 100644
--- a/Part.1.D.preparation.for.reading.ipynb
+++ b/Part.1.D.preparation.for.reading.ipynb
@@ -157,7 +157,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   }
  },
  "nbformat": 4,
diff --git a/Part.1.E.1.entrance.ipynb b/Part.1.E.1.entrance.ipynb
index e28b2c841..28c01e4a1 100644
--- a/Part.1.E.1.entrance.ipynb
+++ b/Part.1.E.1.entrance.ipynb
@@ -121,26 +121,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "False"
-      ]
-     },
-     "execution_count": 2,
-     "metadata": {},
-     "output_type": "execute_result"
-    },
     {
      "data": {
       "text/plain": [
        "True"
       ]
      },
-     "execution_count": 2,
+     "execution_count": 3,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -280,14 +270,14 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 5,
    "metadata": {},
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "693 is odd.\n"
+      "483 is odd.\n"
      ]
     }
    ],
@@ -864,7 +854,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   },
   "toc-autonumbering": true,
   "toc-showmarkdowntxt": false
diff --git a/Part.1.E.2.values-and-their-operators.ipynb b/Part.1.E.2.values-and-their-operators.ipynb
index 220b0dd45..7c4454e5d 100644
--- a/Part.1.E.2.values-and-their-operators.ipynb
+++ b/Part.1.E.2.values-and-their-operators.ipynb
@@ -1131,7 +1131,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   }
  },
  "nbformat": 4,
diff --git a/Part.1.E.3.controlflow.ipynb b/Part.1.E.3.controlflow.ipynb
index b805b7a46..d8ba936f8 100644
--- a/Part.1.E.3.controlflow.ipynb
+++ b/Part.1.E.3.controlflow.ipynb
@@ -1801,7 +1801,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   }
  },
  "nbformat": 4,
diff --git a/Part.1.E.4.functions.ipynb b/Part.1.E.4.functions.ipynb
index 7e8aafdb2..a8648b551 100644
--- a/Part.1.E.4.functions.ipynb
+++ b/Part.1.E.4.functions.ipynb
@@ -698,7 +698,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   },
   "toc-autonumbering": true
  },
diff --git a/Part.1.E.5.strings.ipynb b/Part.1.E.5.strings.ipynb
index 1d80e2361..e59f8462a 100644
--- a/Part.1.E.5.strings.ipynb
+++ b/Part.1.E.5.strings.ipynb
@@ -216,7 +216,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 1,
    "metadata": {},
    "outputs": [
     {
@@ -225,7 +225,7 @@
        "'\\nSimple is better than complex.\\nComplex is better than complicated.\\n'"
       ]
      },
-     "execution_count": 6,
+     "execution_count": 1,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -240,7 +240,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 2,
    "metadata": {},
    "outputs": [
     {
@@ -680,7 +680,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 3,
    "metadata": {},
    "outputs": [
     {
@@ -689,7 +689,7 @@
        "'3.143.143.14'"
       ]
      },
-     "execution_count": 18,
+     "execution_count": 3,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -2746,7 +2746,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   },
   "toc-autonumbering": true
  },
diff --git a/Part.1.F.deal-with-forward-references.ipynb b/Part.1.F.deal-with-forward-references.ipynb
index 8829056e5..1b3f8e6af 100644
--- a/Part.1.F.deal-with-forward-references.ipynb
+++ b/Part.1.F.deal-with-forward-references.ipynb
@@ -391,7 +391,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.1"
+   "version": "3.7.3"
   }
  },
  "nbformat": 4,