{
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   "metadata": {},
   "source": [
    "### <center>San Jose State University<br>Department of Applied Data Science<br><br>**DATA 200<br>Computational Programming for Data Analytics**<br><br>Spring 2023<br>Instructor: Ron Mak</center>"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# 3.6 `if`…`else` and `if`…`elif`…`else` Statements\n",
    "\n",
    "#### The `if`…`else` statement executes one suite or another, depending on whether a condition is `True` or `False`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 85\n",
    "\n",
    "if grade >= 60: \n",
    "    print('Passed!')\n",
    "    print('Great job!')\n",
    "else:\n",
    "    print('Failed!')\n",
    "    print('Too bad.')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 57\n",
    "\n",
    "if grade >= 60: \n",
    "    print('Passed!')\n",
    "    print('Great job!')\n",
    "else:\n",
    "    print('Failed!')\n",
    "    print('Too bad.')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Conditional Expressions\n",
    "\n",
    "#### Suppose you want to store a different value in a variable like `result` based on the value of a condition."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 87\n",
    "\n",
    "if grade >= 60:\n",
    "    result = 'Passed'\n",
    "else:\n",
    "    result = 'Failed'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "result"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### A more consise way to write this is with a **conditional expression**."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "result = ('Passed' if grade >= 60 else 'Failed')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "result"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### The parentheses aren't required, but they make it clearer what you're assigning to `result`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "result = 'Passed' if grade >= 60 else 'Failed'\n",
    "\n",
    "result"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### We can simply display the value of a conditional expression."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 50\n",
    "\n",
    "'Passed' if grade >= 60 else 'Failed'"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### **Yikes!** The following is possible, but maybe it's too hard (for us humans) to read? At least we didn't write it as one long line."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 75\n",
    "\n",
    "letter = 'A' if grade >= 90 \\\n",
    "    else 'B' if grade >= 80 \\\n",
    "    else 'C' if grade >= 70 \\\n",
    "    else 'D' if grade >= 60 \\\n",
    "    else 'F'\n",
    "\n",
    "letter"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Multiple Statements in a Suite"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 49\n",
    "\n",
    "if grade >= 60:\n",
    "    print('Passed')\n",
    "else:\n",
    "    print('Failed')\n",
    "    print('You must take this course again')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 100\n",
    "\n",
    "if grade >= 60:\n",
    "    print('Passed')\n",
    "else:\n",
    "    print('Failed')\n",
    "    print('You must take this course again.')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### `if`…`elif`…`else` Statement\n",
    "\n",
    "#### You can test several conditions in succession."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 67\n",
    "\n",
    "print('Your grade is: ', end='')\n",
    "\n",
    "if grade >= 90:\n",
    "    print('A')\n",
    "    print('Excellent!')\n",
    "elif grade >= 80:\n",
    "    print('B')\n",
    "elif grade >= 70:\n",
    "    print('C')\n",
    "elif grade >= 60:\n",
    "    print('D')\n",
    "    print('Barely passing!')\n",
    "else:\n",
    "    print('F')\n",
    "    print('You must take this course again.')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Notice that we used the `end` **keyword argument** at the end of the first call to `print()`. The default for `print()` is to end each line with a line feed character. Adding `end=''` changes the line ending to an empty character, and therefore there won't be a line feed after printing the string `'Your grade is '`.\n",
    "\n",
    "#### **NOTE:** `end=''` is a keyword argument. It does **not** mean that `end` is a keyword (i.e., it is **not** reserved)."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Be careful to indent your statements properly!"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 99\n",
    "\n",
    "print('Your grade is: ', end='')\n",
    "\n",
    "if grade >= 90:\n",
    "    print('A')\n",
    "    print('Excellent!')\n",
    "elif grade >= 80:\n",
    "    print('B')\n",
    "elif grade >= 70:\n",
    "    print('C')\n",
    "elif grade >= 60:\n",
    "    print('D')\n",
    "    print('Barely passing!')\n",
    "else:\n",
    "    print('F')\n",
    "print('You must take this course again')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Just like the `if` statement, the `else` is optional. But leaving it off may result in a logic error. What happens if the value of `grade` is below 60?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "grade = 50\n",
    "\n",
    "print('Your grade is: ', end='')\n",
    "\n",
    "if grade >= 90:\n",
    "    print('A')\n",
    "elif grade >= 80:\n",
    "    print('B')\n",
    "elif grade >= 70:\n",
    "    print('C')\n",
    "elif grade >= 60:\n",
    "    print('D')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### **EXERCISE:** Why is this wrong?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "if grade >= 90:\n",
    "    print('A')\n",
    "else:\n",
    "    print('Not A or B')\n",
    "elif grade >= 80:\n",
    "    print('B')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "##########################################################################\n",
    "# (C) Copyright 2019 by Deitel & Associates, Inc. and                    #\n",
    "# Pearson Education, Inc. All Rights Reserved.                           #\n",
    "#                                                                        #\n",
    "# DISCLAIMER: The authors and publisher of this book have used their     #\n",
    "# best efforts in preparing the book. These efforts include the          #\n",
    "# development, research, and testing of the theories and programs        #\n",
    "# to determine their effectiveness. The authors and publisher make       #\n",
    "# no warranty of any kind, expressed or implied, with regard to these    #\n",
    "# programs or to the documentation contained in these books. The authors #\n",
    "# and publisher shall not be liable in any event for incidental or       #\n",
    "# consequential damages in connection with, or arising out of, the       #\n",
    "# furnishing, performance, or use of these programs.                     #\n",
    "##########################################################################\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Additional material (C) Copyright 2023 by Ronald Mak\n",
    "# Richter Scale problem based on Python for Everyone by Cay Horstmann and Rance Necaise"
   ]
  }
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