Add code to exercises where it is needed

Author: Nozdi

100 Numpy exercises no solution.ipynb

@@ -275,6 +275,19 @@
     "#### 17. What is the result of the following expression? (★☆☆)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "```python\n",
+    "0 * np.nan\n",
+    "np.nan == np.nan\n",
+    "np.inf > np.nan\n",
+    "np.nan - np.nan\n",
+    "0.3 == 3 * 0.1\n",
+    "```"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -419,6 +432,19 @@
     "#### 26. What is the output of the following script? (★☆☆)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "```python\n",
+    "# Author: Jake VanderPlas\n",
+    "\n",
+    "print(sum(range(5),-1))\n",
+    "from numpy import *\n",
+    "print(sum(range(5),-1))\n",
+    "```"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -435,6 +461,20 @@
     "#### 27. Consider an integer vector Z, which of these expressions are legal? (★☆☆)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "```python\n",
+    "Z**Z\n",
+    "2 << Z >> 2\n",
+    "Z <- Z\n",
+    "1j*Z\n",
+    "Z/1/1\n",
+    "Z<Z>Z\n",
+    "```"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -451,6 +491,17 @@
     "#### 28. What are the result of the following expressions?"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "```python\n",
+    "np.array(0) / np.array(0)\n",
+    "np.array(0) // np.array(0)\n",
+    "np.array([np.nan]).astype(int).astype(float)\n",
+    "```"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -515,6 +566,15 @@
     "#### 32. Is the following expressions true? (★☆☆)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "```python\n",
+    "np.sqrt(-1) == np.emath.sqrt(-1)\n",
+    "```"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -867,6 +927,17 @@
     "#### 54. How to read the following file? (★★☆)"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "```\n",
+    "1, 2, 3, 4, 5\n",
+    "6,  ,  , 7, 8\n",
+    " ,  , 9,10,11\n",
+    "```"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,