03_-_functions.ipynb

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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Importing specific functions from a module is possible.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "from math import sqrt\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Entire module can be imported as well.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "import math\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Some functions are available natively in Python.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3"
      ]
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     "execution_count": 3,
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   "source": [
    "a = [1, 2, 3]\n",
    "\n",
    "len(a)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "\"sqrt\" function can be called upon a number to get its square root.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "2.0"
      ]
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     "execution_count": 4,
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   "source": [
    "sqrt(4)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Number \"pi\" can be accessed via \"math\" library.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "3.141592653589793\n"
     ]
    }
   ],
   "source": [
    "print(math.pi)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "New functions can be defined as well.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Running \"func_1\".\n"
     ]
    }
   ],
   "source": [
    "\n",
    "def func_1():\n",
    "\n",
    "    print(\"Running \\\"func_1\\\".\")\n",
    "\n",
    "\n",
    "func_1()\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Note that to \"call\" or \"invoke\" a function we need to use the \"()\". Calling the function without \"()\" will only give its memory location.\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Arguments can be passed to the function. Annotations can be used to tell the function what are the expected argument types.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "6\n"
     ]
    }
   ],
   "source": [
    "def func_2(a: int, b: int):\n",
    "\n",
    "    return a * b\n",
    "\n",
    "\n",
    "print(func_2(2, 3))\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Still, any argument type can still be passed to the function.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "aaa\n"
     ]
    }
   ],
   "source": [
    "print(func_2(\"a\", 3))\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Even lists can be used as input.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[1, 2, 1, 2, 1, 2]\n"
     ]
    }
   ],
   "source": [
    "print(func_2([1, 2], 3))\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "However, strings are not supported by the \"\\*\" operator. The next line is commented because it would throw an error otherwise.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [],
   "source": [
    "# print(func_2(\"a\", \"b\"))\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Calling the function without any arguments will just print its definition and memory location.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "<function func_2 at 0x000001F1A9B62280>\n"
     ]
    }
   ],
   "source": [
    "print(func_2)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Functions can call other functions in their execution.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Running func_4\n"
     ]
    }
   ],
   "source": [
    "def func_3():\n",
    "\n",
    "    return func_4()\n",
    "\n",
    "\n",
    "def func_4():\n",
    "\n",
    "    return print(\"Running func_4\")\n",
    "\n",
    "\n",
    "func_3()\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Still, the proper order of execution is essential when it comes to running the code. The next lines are commented because they would throw an error otherwise.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [],
   "source": [
    "# def func_5():\n",
    "\n",
    "#     return func_6()\n",
    "\n",
    "\n",
    "# func_5()\n",
    "\n",
    "\n",
    "# def func_6():\n",
    "\n",
    "#     return print(\"Running func_5\")\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "It is possible to run lambda functions in Python.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "4\n"
     ]
    }
   ],
   "source": [
    "def fn1(x): return x**2\n",
    "\n",
    "\n",
    "print(fn1(2))\n"
   ]
  }
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