diff --git a/module3/exo1/analyse-syndrome-grippal.ipynb b/module3/exo1/analyse-syndrome-grippal.ipynb
index 59d72b5b58a3ae26346460dd39e62a39c55243d7..17d7e423139d6383268fbfd081a847b5988cc1dd 100644
--- a/module3/exo1/analyse-syndrome-grippal.ipynb
+++ b/module3/exo1/analyse-syndrome-grippal.ipynb
@@ -34,7 +34,8 @@
    },
    "outputs": [],
    "source": [
-    "data_url = \"http://www.sentiweb.fr/datasets/incidence-PAY-3.csv\""
+    "data_url = \"http://www.sentiweb.fr/datasets/incidence-PAY-3.csv\"\n",
+    "local_filename = \"incidence-PAY-3.csv\""
    ]
   },
   {
@@ -65,7 +66,19 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "raw_data = pd.read_csv(data_url, skiprows=1)\n",
+    "if not os.path.exists(local_filename):\n",
+    "    raw_data = pd.read_csv(data_url, skiprows=1)\n",
+    "    raw_data.to_csv(local_filename, index=False)  \n",
+    "else:\n",
+    "    raw_data = pd.read_csv(local_filename)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
     "raw_data"
    ]
   },
@@ -278,12 +291,14 @@
    "metadata": {},
    "outputs": [],
    "source": [
+    "first_august_week = [pd.Period(pd.Timestamp(y, 8, 1), 'W')\n",
+    "                     for y in range(1985, sorted_data.index[-1].year)]\n",
+    "\n",
     "year = []\n",
     "yearly_incidence = []\n",
-    "for week1, week2 in zip(first_august_week[:-1],\n",
-    "                        first_august_week[1:]):\n",
+    "for week1, week2 in zip(first_august_week[:-1], first_august_week[1:]):\n",
     "    one_year = sorted_data['inc'][week1:week2-1]\n",
-    "    assert abs(len(one_year)-52) < 2\n",
+    "    assert abs(len(one_year) - 52) < 2\n",
     "    yearly_incidence.append(one_year.sum())\n",
     "    year.append(week2.year)\n",
     "yearly_incidence = pd.Series(data=yearly_incidence, index=year)"
@@ -337,15 +352,6 @@
    "source": [
     "yearly_incidence.hist(xrot=20)"
    ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {
-    "collapsed": true
-   },
-   "outputs": [],
-   "source": []
   }
  ],
  "metadata": {
@@ -364,7 +370,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.6.1"
+   "version": "3.6.4"
   }
  },
  "nbformat": 4,