{
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   "source": [
    "## `dtype`"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7c7f69f2",
   "metadata": {},
   "source": [
    "`ndarray` is a container for homogeneous data, i.e. all elements must be of the same type. Each array has a `dtype`, an object that describes the data type of the array:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "04e4b903",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "dtype('float64')"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "import numpy as np\n",
    "\n",
    "\n",
    "data = np.random.randn(7, 3)\n",
    "dt = data.dtype\n",
    "dt"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "2a09a4c5",
   "metadata": {},
   "source": [
    "NumPy data types:\n",
    "\n",
    "Type              | Type code     | Description\n",
    ":---------------- | :------------ | :----------\n",
    "`int8`, `uint8`   | `i1`, `u1`    | Signed and unsigned 8-bit (1-byte) integer types\n",
    "`int16`, `uint16` | `i2`, `u2`    | Signed and unsigned 16-Bit (2 Byte) integer types\n",
    "`int32`, `uint32` | `i4`, `u4`    | Signed and unsigned 32-Bit (4 Byte) integer types\n",
    "`int64`, `uint64` | `i8`, `u8`    | Signed and unsigned 64-Bit (8 Byte) integer types\n",
    "`float16`         | `f2`          | Standard floating point with half precision\n",
    "`float32`         | `f4` or `f`   | Standard floating point with single precision; compatible with C `float`\n",
    "`float64`         | `f8` or `d`   | Standard floating point with double precision; compatible with C `double` and Python `float` object\n",
    "`complex64`, `complex128`, `complex256` | `c8`, `c16`, `c32` | Complex numbers represented by two 32, 64 or 128 floating point numbers respectively\n",
    "`bool`            | `?`           | Boolean type that stores the values `True` and `False`\n",
    "`object`          | `O`           | Python object type; a value can be any Python object\n",
    "`string_`         | `S`           | ASCII string type with fixed length (1 byte per character); to create a string type with length 7, for example, use `S7`; longer inputs are truncated without warning\n",
    "`unicode_`        | `U`           | Unicode type with fixed length where the number of bytes is platform-specific; uses the same specification semantics as `string_`, e.g. `U7`"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "f4a0b6b2",
   "metadata": {},
   "source": [
    "Determine the number of elements with `itemsize`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "ba581655",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "8"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dt.itemsize"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "4bc3981f",
   "metadata": {},
   "source": [
    "Determine the name of the data type:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "465e5fbd",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'float64'"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dt.name"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e1bbf89d",
   "metadata": {},
   "source": [
    "Check data type:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "b8771580",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dt.type is np.float64"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8d304951",
   "metadata": {},
   "source": [
    "Change data type with `astype`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "372a4baf",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[ 0.44477868,  1.7366465 , -2.0396285 ],\n",
       "       [ 0.65273875, -0.11706501, -2.3253074 ],\n",
       "       [-1.3416812 , -1.1469622 ,  0.04803479],\n",
       "       [-0.08298384, -0.02865864,  1.0284923 ],\n",
       "       [ 0.59293705,  0.5345401 , -1.717722  ],\n",
       "       [-1.1971567 , -0.4091349 , -0.03829814],\n",
       "       [ 1.030255  ,  0.9890015 , -0.4749484 ]], dtype=float32)"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "data_float32 = data.astype(np.float32)\n",
    "data_float32"
   ]
  }
 ],
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