Tweak Ex 31 in the notebook too

100 Numpy exercises.ipynb

@@ -477,8 +477,8 @@
    "outputs": [],
    "source": [
     "Z = np.dot(np.ones((5,3)), np.ones((3,2)))\n",
-    "print(Z)",
-    "\n\n",
+    "print(Z)\n",
+    "\n",
     "# Alternative solution, in Python 3.5 and above\n",
     "Z = np.ones((5,3)) @ np.ones((3,2))"
    ]
@@ -631,7 +631,13 @@
     "Z = np.ones(1) / 0\n",
     "\n",
     "# Back to sanity\n",
-    "_ = np.seterr(**defaults)"
+    "_ = np.seterr(**defaults)\n",
+    "\n",
+    "An equivalent way, with a context manager:\n",
+    "\n",
+    "```python\n",
+    "with np.errstate(divide='ignore'):\n",
+    "    Z = np.ones(1) / 0"
    ]
   },
   {
@@ -2334,7 +2340,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.5.2"
+   "version": "3.5.1"
   }
  },
  "nbformat": 4,