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  {
   "cell_type": "code",
   "execution_count": null,
   "id": "documentary-joint",
   "metadata": {},
   "outputs": [],
   "source": [
    "# This tutorial will introduce simple implementations of conditional if\n",
    "# statements in Python."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "muslim-imaging",
   "metadata": {},
   "outputs": [],
   "source": [
    "# Here's a simple if statement.  If statements use the same indentation\n",
    "# scheme as for loops.  Indented lines immediately following the if \n",
    "# statement are within the if control sturcture.  The if statement ends\n",
    "# when the indented block of code ends.\n",
    "ans = 'y'\n",
    "if ans == 'y':\n",
    "    print('yes')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "entitled-vegetable",
   "metadata": {},
   "outputs": [],
   "source": [
    "# In the example above, ans was set equal to 'y' and the if condition was\n",
    "# true such that 'yes' was printed.  In the example below, ans is not equal\n",
    "# to 'y' and the if condition is false.  As a result, no output is printed.\n",
    "ans = 'n'\n",
    "if ans == 'y':\n",
    "    print('yes')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "floral-channels",
   "metadata": {},
   "outputs": [],
   "source": [
    "# We can enhance the capability of our if statement by adding an else\n",
    "# statement.  Anytime the if condition is false, the else statement will\n",
    "# execute.\n",
    "\n",
    "# True, so 'yes' output.\n",
    "ans = 'y'\n",
    "if ans == 'y':\n",
    "    print('yes')\n",
    "else:\n",
    "    print('no')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "raising-puzzle",
   "metadata": {},
   "outputs": [],
   "source": [
    "# False, so 'no' output.\n",
    "ans = 'n'\n",
    "if ans == 'y':\n",
    "    print('yes')\n",
    "else:\n",
    "    print('no')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "figured-tribe",
   "metadata": {},
   "outputs": [],
   "source": [
    "# False, so 'no' output.\n",
    "ans = 'x'\n",
    "if ans == 'y':\n",
    "    print('yes')\n",
    "else:\n",
    "    print('no')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "happy-circumstances",
   "metadata": {},
   "outputs": [],
   "source": [
    "# In the above if statement the only \"y\" produces a \"yes\", any other entry\n",
    "# results in \"no\".  Suppose that you only want to accept \"y\" and \"n\" as\n",
    "# valid responses.  Including an 'else if' condtion (using 'elif') as done \n",
    "# below produces the desired results."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "endangered-worth",
   "metadata": {},
   "outputs": [],
   "source": [
    "# If condition true, so output 'yes'.\n",
    "ans = 'y'\n",
    "if ans == 'y':\n",
    "    print('yes')\n",
    "elif ans == 'n':\n",
    "    print('no')\n",
    "else:\n",
    "    print('invalid response')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "dietary-cornwall",
   "metadata": {},
   "outputs": [],
   "source": [
    "# Elseif condition true, so output 'no'.\n",
    "ans = 'n';\n",
    "if ans == 'y':\n",
    "    print('yes')\n",
    "elif ans == 'n':\n",
    "    print('no')\n",
    "else:\n",
    "    print('invalid response')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "capable-blind",
   "metadata": {},
   "outputs": [],
   "source": [
    "# If and elseif conditions false, so output 'invalid response'.\n",
    "ans = 'x';\n",
    "if ans == 'y':\n",
    "    print('yes')\n",
    "elif ans == 'n':\n",
    "    print('no')\n",
    "else:\n",
    "    print('invalid response')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "id": "modified-vitamin",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter your value: physics\n",
      "invalid response\n"
     ]
    }
   ],
   "source": [
    "# To complete this tutorial, here's how you can prompt the user for an\n",
    "# input in Python.  All you need to do is use the 'input()' statement.\n",
    "val = input(\"Enter your value: \") \n",
    "if val == 'y':\n",
    "    print('yes')\n",
    "elif val == 'n':\n",
    "    print('no')\n",
    "else:\n",
    "    print('invalid response')"
   ]
  }
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