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    "# Lesson 3 exercises\n",
    "\n",
    "*Because your GitHub teams are not yet assembled, for these exercises, submit your responses via email written to all seven of the course staff.*\n",
    "\n",
    "<hr>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercise 3.1\n",
    "\n",
    "Describe in words the difference between a mutable and immutable object.\n",
    "\n",
    "<br />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercise 3.2\n",
    "\n",
    "**a)** Describe in words the difference between the `==` operator and the `is` operator.\n",
    "\n",
    "**b)** Why should you not use the `==` operator to compare two `float`s?\n",
    "\n",
    "<br />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercise 3.3\n",
    "\n",
    "*Do this before Exercise 3.4.* Without running the code, write what will be printed for the following Python codes.\n",
    "\n",
    "**a)**\n",
    "```python\n",
    "my_list = [1, 2, 3]\n",
    "my_list[2] = \"four\"\n",
    "\n",
    "print(my_list)\n",
    "```\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "**b)**\n",
    "```python\n",
    "a = 5\n",
    "b = 2\n",
    "a = b\n",
    "\n",
    "print(a, b)\n",
    "```\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "\n",
    "**c)**\n",
    "```python\n",
    "def first_element_103(x):\n",
    "    x[0] = 103\n",
    "    \n",
    "x = [1, 2, 3]\n",
    "\n",
    "first_element_103(x)\n",
    "\n",
    "print(x)\n",
    "```\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "\n",
    "\n",
    "**d)**\n",
    "```python\n",
    "def add_103(x):\n",
    "    x += 103\n",
    "    \n",
    "x = 4\n",
    "\n",
    "add_103(x)\n",
    "\n",
    "print(x)\n",
    "```\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "\n",
    "**e)**\n",
    "```python\n",
    "def add_103(x):\n",
    "    return x + 103\n",
    "    \n",
    "x = 4\n",
    "\n",
    "x = add_103(x)\n",
    "\n",
    "print(x)\n",
    "```\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**f)**\n",
    "```python\n",
    "def append_103(x):\n",
    "    x.append(103)\n",
    "    \n",
    "a = [1, 2, 3]\n",
    "b = a\n",
    "\n",
    "append_103(b)\n",
    "\n",
    "print(a)\n",
    "```\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "\n",
    "**g)**\n",
    "```python\n",
    "add_three_numbers = lambda x, y, z: x + y + z\n",
    "\n",
    "print(add_three_numbers(*(5, 6, 7)))\n",
    "```\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "\n",
    "**h)**\n",
    "```python\n",
    "print([i for i in range(1, 10) if i % 2])\n",
    "```\n",
    "\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "\n",
    "**i)** As we will learn when we learn about style, you should not write code like this example; it's overly tricky to read. But it will help see if you understand how list comprehensions work.\n",
    "```python\n",
    "print([i if i % 3 == 0 else i**2 for i in range(1, 10) if i % 2])\n",
    "```\n",
    "\n",
    "\n",
    "<hr>\n",
    "<br />\n",
    "\n",
    "**j)** This one is tricky. Don't worry if you have trouble with this.\n",
    "\n",
    "```python\n",
    "def append_103(x=[]):\n",
    "    x.append(103)\n",
    "\n",
    "    return x\n",
    "\n",
    "append_103()\n",
    "append_103()\n",
    "append_103()\n",
    "\n",
    "print(append_103())\n",
    "```\n",
    "\n",
    "<br />"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercise 3.4\n",
    "\n",
    "Check your work from Exercise 3.3 by running the codes in code cells. *Do not* change your answers to Exercise 3.3 after doing this.\n",
    "\n",
    "<br />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercise 3.5\n",
    "\n",
    "What is the difference between a key and a value in a dictionary?\n",
    "\n",
    "<br />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercise 3.6\n",
    "\n",
    "Can a dictionary have duplicate keys? Can it have duplicate values?\n",
    "\n",
    "<br />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Exercise 3.7 (optional)\n",
    "\n",
    "Write down any questions or points of confusion that you have."
   ]
  }
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