530_Dunder_Methods.ipynb

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   "cell_type": "markdown",
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   "source": [
    "# Dunder Methods\n",
    "\n",
    "Dunder methods, also known as \"magic methods\" start with and end with two underscores. A double underscore, or dunder for short, are Python built-in methods on classes. \n",
    "\n",
    "There are quite a few dunder methods available, but these are the most common ones you'll generally see."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "metadata": {},
   "outputs": [],
   "source": [
    "class Book:\n",
    "    \n",
    "    def __init__(self, title, pages, content):\n",
    "        self.title = title\n",
    "        self.pages = int(pages)\n",
    "        self.content = content \n",
    "        \n",
    "    def __str__(self):\n",
    "        return self.title\n",
    "    \n",
    "    def __len__(self):\n",
    "        words = self.content.split(' ')\n",
    "        return len(words)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [],
   "source": [
    "harry_potter = Book(\"Harry Potter\", 250, \"Lorem ipsum dolor sit amet, consectetur adipisicing elit. Veniam laboriosam consequatur saepe. Repellat itaque dolores neque, impedit reprehenderit eum culpa voluptates harum sapiente nesciunt ratione.\")"
   ]
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   "cell_type": "code",
   "execution_count": 36,
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       "25"
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     "execution_count": 36,
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   "source": [
    "len(harry_potter)"
   ]
  },
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     "name": "stdout",
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     "text": [
      "Help on int object:\n",
      "\n",
      "class int(object)\n",
      " |  int([x]) -> integer\n",
      " |  int(x, base=10) -> integer\n",
      " |  \n",
      " |  Convert a number or string to an integer, or return 0 if no arguments\n",
      " |  are given.  If x is a number, return x.__int__().  For floating point\n",
      " |  numbers, this truncates towards zero.\n",
      " |  \n",
      " |  If x is not a number or if base is given, then x must be a string,\n",
      " |  bytes, or bytearray instance representing an integer literal in the\n",
      " |  given base.  The literal can be preceded by '+' or '-' and be surrounded\n",
      " |  by whitespace.  The base defaults to 10.  Valid bases are 0 and 2-36.\n",
      " |  Base 0 means to interpret the base from the string as an integer literal.\n",
      " |  >>> int('0b100', base=0)\n",
      " |  4\n",
      " |  \n",
      " |  Methods defined here:\n",
      " |  \n",
      " |  __abs__(self, /)\n",
      " |      abs(self)\n",
      " |  \n",
      " |  __add__(self, value, /)\n",
      " |      Return self+value.\n",
      " |  \n",
      " |  __and__(self, value, /)\n",
      " |      Return self&value.\n",
      " |  \n",
      " |  __bool__(self, /)\n",
      " |      self != 0\n",
      " |  \n",
      " |  __ceil__(...)\n",
      " |      Ceiling of an Integral returns itself.\n",
      " |  \n",
      " |  __divmod__(self, value, /)\n",
      " |      Return divmod(self, value).\n",
      " |  \n",
      " |  __eq__(self, value, /)\n",
      " |      Return self==value.\n",
      " |  \n",
      " |  __float__(self, /)\n",
      " |      float(self)\n",
      " |  \n",
      " |  __floor__(...)\n",
      " |      Flooring an Integral returns itself.\n",
      " |  \n",
      " |  __floordiv__(self, value, /)\n",
      " |      Return self//value.\n",
      " |  \n",
      " |  __format__(self, format_spec, /)\n",
      " |      Default object formatter.\n",
      " |  \n",
      " |  __ge__(self, value, /)\n",
      " |      Return self>=value.\n",
      " |  \n",
      " |  __getattribute__(self, name, /)\n",
      " |      Return getattr(self, name).\n",
      " |  \n",
      " |  __getnewargs__(self, /)\n",
      " |  \n",
      " |  __gt__(self, value, /)\n",
      " |      Return self>value.\n",
      " |  \n",
      " |  __hash__(self, /)\n",
      " |      Return hash(self).\n",
      " |  \n",
      " |  __index__(self, /)\n",
      " |      Return self converted to an integer, if self is suitable for use as an index into a list.\n",
      " |  \n",
      " |  __int__(self, /)\n",
      " |      int(self)\n",
      " |  \n",
      " |  __invert__(self, /)\n",
      " |      ~self\n",
      " |  \n",
      " |  __le__(self, value, /)\n",
      " |      Return self<=value.\n",
      " |  \n",
      " |  __lshift__(self, value, /)\n",
      " |      Return self<<value.\n",
      " |  \n",
      " |  __lt__(self, value, /)\n",
      " |      Return self<value.\n",
      " |  \n",
      " |  __mod__(self, value, /)\n",
      " |      Return self%value.\n",
      " |  \n",
      " |  __mul__(self, value, /)\n",
      " |      Return self*value.\n",
      " |  \n",
      " |  __ne__(self, value, /)\n",
      " |      Return self!=value.\n",
      " |  \n",
      " |  __neg__(self, /)\n",
      " |      -self\n",
      " |  \n",
      " |  __or__(self, value, /)\n",
      " |      Return self|value.\n",
      " |  \n",
      " |  __pos__(self, /)\n",
      " |      +self\n",
      " |  \n",
      " |  __pow__(self, value, mod=None, /)\n",
      " |      Return pow(self, value, mod).\n",
      " |  \n",
      " |  __radd__(self, value, /)\n",
      " |      Return value+self.\n",
      " |  \n",
      " |  __rand__(self, value, /)\n",
      " |      Return value&self.\n",
      " |  \n",
      " |  __rdivmod__(self, value, /)\n",
      " |      Return divmod(value, self).\n",
      " |  \n",
      " |  __repr__(self, /)\n",
      " |      Return repr(self).\n",
      " |  \n",
      " |  __rfloordiv__(self, value, /)\n",
      " |      Return value//self.\n",
      " |  \n",
      " |  __rlshift__(self, value, /)\n",
      " |      Return value<<self.\n",
      " |  \n",
      " |  __rmod__(self, value, /)\n",
      " |      Return value%self.\n",
      " |  \n",
      " |  __rmul__(self, value, /)\n",
      " |      Return value*self.\n",
      " |  \n",
      " |  __ror__(self, value, /)\n",
      " |      Return value|self.\n",
      " |  \n",
      " |  __round__(...)\n",
      " |      Rounding an Integral returns itself.\n",
      " |      Rounding with an ndigits argument also returns an integer.\n",
      " |  \n",
      " |  __rpow__(self, value, mod=None, /)\n",
      " |      Return pow(value, self, mod).\n",
      " |  \n",
      " |  __rrshift__(self, value, /)\n",
      " |      Return value>>self.\n",
      " |  \n",
      " |  __rshift__(self, value, /)\n",
      " |      Return self>>value.\n",
      " |  \n",
      " |  __rsub__(self, value, /)\n",
      " |      Return value-self.\n",
      " |  \n",
      " |  __rtruediv__(self, value, /)\n",
      " |      Return value/self.\n",
      " |  \n",
      " |  __rxor__(self, value, /)\n",
      " |      Return value^self.\n",
      " |  \n",
      " |  __sizeof__(self, /)\n",
      " |      Returns size in memory, in bytes.\n",
      " |  \n",
      " |  __str__(self, /)\n",
      " |      Return str(self).\n",
      " |  \n",
      " |  __sub__(self, value, /)\n",
      " |      Return self-value.\n",
      " |  \n",
      " |  __truediv__(self, value, /)\n",
      " |      Return self/value.\n",
      " |  \n",
      " |  __trunc__(...)\n",
      " |      Truncating an Integral returns itself.\n",
      " |  \n",
      " |  __xor__(self, value, /)\n",
      " |      Return self^value.\n",
      " |  \n",
      " |  bit_length(self, /)\n",
      " |      Number of bits necessary to represent self in binary.\n",
      " |      \n",
      " |      >>> bin(37)\n",
      " |      '0b100101'\n",
      " |      >>> (37).bit_length()\n",
      " |      6\n",
      " |  \n",
      " |  conjugate(...)\n",
      " |      Returns self, the complex conjugate of any int.\n",
      " |  \n",
      " |  to_bytes(self, /, length, byteorder, *, signed=False)\n",
      " |      Return an array of bytes representing an integer.\n",
      " |      \n",
      " |      length\n",
      " |        Length of bytes object to use.  An OverflowError is raised if the\n",
      " |        integer is not representable with the given number of bytes.\n",
      " |      byteorder\n",
      " |        The byte order used to represent the integer.  If byteorder is 'big',\n",
      " |        the most significant byte is at the beginning of the byte array.  If\n",
      " |        byteorder is 'little', the most significant byte is at the end of the\n",
      " |        byte array.  To request the native byte order of the host system, use\n",
      " |        `sys.byteorder' as the byte order value.\n",
      " |      signed\n",
      " |        Determines whether two's complement is used to represent the integer.\n",
      " |        If signed is False and a negative integer is given, an OverflowError\n",
      " |        is raised.\n",
      " |  \n",
      " |  ----------------------------------------------------------------------\n",
      " |  Class methods defined here:\n",
      " |  \n",
      " |  from_bytes(bytes, byteorder, *, signed=False) from builtins.type\n",
      " |      Return the integer represented by the given array of bytes.\n",
      " |      \n",
      " |      bytes\n",
      " |        Holds the array of bytes to convert.  The argument must either\n",
      " |        support the buffer protocol or be an iterable object producing bytes.\n",
      " |        Bytes and bytearray are examples of built-in objects that support the\n",
      " |        buffer protocol.\n",
      " |      byteorder\n",
      " |        The byte order used to represent the integer.  If byteorder is 'big',\n",
      " |        the most significant byte is at the beginning of the byte array.  If\n",
      " |        byteorder is 'little', the most significant byte is at the end of the\n",
      " |        byte array.  To request the native byte order of the host system, use\n",
      " |        `sys.byteorder' as the byte order value.\n",
      " |      signed\n",
      " |        Indicates whether two's complement is used to represent the integer.\n",
      " |  \n",
      " |  ----------------------------------------------------------------------\n",
      " |  Static methods defined here:\n",
      " |  \n",
      " |  __new__(*args, **kwargs) from builtins.type\n",
      " |      Create and return a new object.  See help(type) for accurate signature.\n",
      " |  \n",
      " |  ----------------------------------------------------------------------\n",
      " |  Data descriptors defined here:\n",
      " |  \n",
      " |  denominator\n",
      " |      the denominator of a rational number in lowest terms\n",
      " |  \n",
      " |  imag\n",
      " |      the imaginary part of a complex number\n",
      " |  \n",
      " |  numerator\n",
      " |      the numerator of a rational number in lowest terms\n",
      " |  \n",
      " |  real\n",
      " |      the real part of a complex number\n",
      "\n"
     ]
    }
   ],
   "source": [
    "help(harry_potter.__sizeof__())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "metadata": {},
   "outputs": [],
   "source": [
    "lotr = Book(\"Lord of the Rings\", 900, \".........\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 43,
   "metadata": {
    "scrolled": true
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Lord of the Rings\n"
     ]
    }
   ],
   "source": [
    "print(lotr)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "metadata": {},
   "outputs": [],
   "source": [
    "del lotr"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "metadata": {},
   "outputs": [
    {
     "ename": "NameError",
     "evalue": "name 'lotr' is not defined",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-45-7a6a068e64da>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mlotr\u001b[0m\u001b[0;34m\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m",
      "\u001b[0;31mNameError\u001b[0m: name 'lotr' is not defined"
     ]
    }
   ],
   "source": [
    "lotr"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "> **Note:** We used `del` to delete the variable `lotr` which was holding an entire Book() class worth of data. "
   ]
  }
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