ch02.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import numpy as np\n",
    "np.random.seed(12345)\n",
    "np.set_printoptions(precision=4, suppress=True)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[-0.20470765948471295,\n",
       " 0.47894333805754824,\n",
       " -0.5194387150567381,\n",
       " -0.55573030434749,\n",
       " 1.9657805725027142,\n",
       " 1.3934058329729904,\n",
       " 0.09290787674371767]"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "import numpy as np\n",
    "data = [np.random.standard_normal() for i in range(7)]\n",
    "data"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [],
   "source": [
    "# assigning a variable, creates a reference to the object\n",
    "\n",
    "a = [1, 2, 3]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [],
   "source": [
    "b = a\n",
    "b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\u001b[0;31mType:\u001b[0m        list\n",
      "\u001b[0;31mString form:\u001b[0m [1, 2, 3]\n",
      "\u001b[0;31mLength:\u001b[0m      3\n",
      "\u001b[0;31mDocstring:\u001b[0m  \n",
      "Built-in mutable sequence.\n",
      "\n",
      "If no argument is given, the constructor creates a new empty list.\n",
      "The argument must be an iterable if specified."
     ]
    }
   ],
   "source": [
    "a?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "# reference to the same object (binding a name to an object)\n",
    "\n",
    "a.append(4)\n",
    "b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [],
   "source": [
    "# passing objects as arguments to a function, creates a new local variable referencing the object without copying\n",
    "\n",
    "def append_element(some_list, element):\n",
    "    some_list.append(element)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [],
   "source": [
    "data = [1, 2, 3]\n",
    "append_element(data, 4)\n",
    "data"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [],
   "source": [
    "# to check object's type\n",
    "a = 5\n",
    "type(a)\n",
    "a = \"foo\"\n",
    "type(a)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [],
   "source": [
    "\"5\" + 5"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = 4.5\n",
    "b = 2\n",
    "# String formatting, to be visited later\n",
    "print(f\"a is {type(a)}, b is {type(b)}\")\n",
    "a / b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = 5\n",
    "isinstance(a, int)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = 5; b = 4.5\n",
    "isinstance(a, (int, float))\n",
    "isinstance(b, (int, float))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = \"foo\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [],
   "source": [
    "getattr(a, \"split\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [],
   "source": [
    "def isiterable(obj):\n",
    "    try:\n",
    "        iter(obj)\n",
    "        return True\n",
    "    except TypeError: # not iterable\n",
    "        return False"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [],
   "source": [
    "isiterable(\"a string\")\n",
    "isiterable([1, 2, 3])\n",
    "isiterable(5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [],
   "source": [
    "5 - 7\n",
    "12 + 21.5\n",
    "5 <= 2"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = [1, 2, 3]\n",
    "b = a\n",
    "c = list(a)\n",
    "a is b\n",
    "a is not c"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {},
   "outputs": [],
   "source": [
    "a == c"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = None\n",
    "a is None"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [],
   "source": [
    "a_list = [\"foo\", 2, [4, 5]]\n",
    "a_list[2] = (3, 4)\n",
    "a_list"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {},
   "outputs": [],
   "source": [
    "a_tuple = (3, 5, (4, 5))\n",
    "a_tuple[1] = \"four\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {},
   "outputs": [],
   "source": [
    "ival = 17239871\n",
    "ival ** 6"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {},
   "outputs": [],
   "source": [
    "fval = 7.243\n",
    "fval2 = 6.78e-5"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {},
   "outputs": [],
   "source": [
    "3 / 2"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {},
   "outputs": [],
   "source": [
    "3 // 2"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {},
   "outputs": [],
   "source": [
    "c = \"\"\"\n",
    "This is a longer string that\n",
    "spans multiple lines\n",
    "\"\"\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {},
   "outputs": [],
   "source": [
    "c.count(\"\\n\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = \"this is a string\"\n",
    "a[10] = \"f\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {},
   "outputs": [],
   "source": [
    "b = a.replace(\"string\", \"longer string\")\n",
    "b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 31,
   "metadata": {},
   "outputs": [],
   "source": [
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = 5.6\n",
    "s = str(a)\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "metadata": {},
   "outputs": [],
   "source": [
    "s = \"python\"\n",
    "list(s)\n",
    "s[:3]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "metadata": {},
   "outputs": [],
   "source": [
    "s = \"12\\\\34\"\n",
    "print(s)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 35,
   "metadata": {},
   "outputs": [],
   "source": [
    "s = r\"this\\has\\no\\special\\characters\"\n",
    "s"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = \"this is the first half \"\n",
    "b = \"and this is the second half\"\n",
    "a + b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 37,
   "metadata": {},
   "outputs": [],
   "source": [
    "template = \"{0:.2f} {1:s} are worth US${2:d}\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 38,
   "metadata": {},
   "outputs": [],
   "source": [
    "template.format(88.46, \"Argentine Pesos\", 1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 39,
   "metadata": {},
   "outputs": [],
   "source": [
    "amount = 10\n",
    "rate = 88.46\n",
    "currency = \"Pesos\"\n",
    "result = f\"{amount} {currency} is worth US${amount / rate}\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 40,
   "metadata": {},
   "outputs": [],
   "source": [
    "f\"{amount} {currency} is worth US${amount / rate:.2f}\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 41,
   "metadata": {},
   "outputs": [],
   "source": [
    "val = \"español\"\n",
    "val"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "metadata": {},
   "outputs": [],
   "source": [
    "val_utf8 = val.encode(\"utf-8\")\n",
    "val_utf8\n",
    "type(val_utf8)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 43,
   "metadata": {},
   "outputs": [],
   "source": [
    "val_utf8.decode(\"utf-8\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "metadata": {},
   "outputs": [],
   "source": [
    "val.encode(\"latin1\")\n",
    "val.encode(\"utf-16\")\n",
    "val.encode(\"utf-16le\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "metadata": {},
   "outputs": [],
   "source": [
    "True and True\n",
    "False or True"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "metadata": {},
   "outputs": [],
   "source": [
    "int(False)\n",
    "int(True)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 47,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = True\n",
    "b = False\n",
    "not a\n",
    "not b"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 48,
   "metadata": {},
   "outputs": [],
   "source": [
    "s = \"3.14159\"\n",
    "fval = float(s)\n",
    "type(fval)\n",
    "int(fval)\n",
    "bool(fval)\n",
    "bool(0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 49,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = None\n",
    "a is None\n",
    "b = 5\n",
    "b is not None"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 50,
   "metadata": {},
   "outputs": [],
   "source": [
    "from datetime import datetime, date, time\n",
    "dt = datetime(2011, 10, 29, 20, 30, 21)\n",
    "dt.day\n",
    "dt.minute"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 51,
   "metadata": {},
   "outputs": [],
   "source": [
    "dt.date()\n",
    "dt.time()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 52,
   "metadata": {},
   "outputs": [],
   "source": [
    "dt.strftime(\"%Y-%m-%d %H:%M\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 53,
   "metadata": {},
   "outputs": [],
   "source": [
    "datetime.strptime(\"20091031\", \"%Y%m%d\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 54,
   "metadata": {},
   "outputs": [],
   "source": [
    "dt_hour = dt.replace(minute=0, second=0)\n",
    "dt_hour"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 55,
   "metadata": {},
   "outputs": [],
   "source": [
    "dt"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 56,
   "metadata": {},
   "outputs": [],
   "source": [
    "dt2 = datetime(2011, 11, 15, 22, 30)\n",
    "delta = dt2 - dt\n",
    "delta\n",
    "type(delta)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 57,
   "metadata": {},
   "outputs": [],
   "source": [
    "dt\n",
    "dt + delta"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 58,
   "metadata": {},
   "outputs": [],
   "source": [
    "a = 5; b = 7\n",
    "c = 8; d = 4\n",
    "if a < b or c > d:\n",
    "    print(\"Made it\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 59,
   "metadata": {},
   "outputs": [],
   "source": [
    "4 > 3 > 2 > 1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 60,
   "metadata": {},
   "outputs": [],
   "source": [
    "for i in range(4):\n",
    "    for j in range(4):\n",
    "        if j > i:\n",
    "            break\n",
    "        print((i, j))\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 61,
   "metadata": {},
   "outputs": [],
   "source": [
    "range(10)\n",
    "list(range(10))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 62,
   "metadata": {},
   "outputs": [],
   "source": [
    "list(range(0, 20, 2))\n",
    "list(range(5, 0, -1))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 63,
   "metadata": {},
   "outputs": [],
   "source": [
    "seq = [1, 2, 3, 4]\n",
    "for i in range(len(seq)):\n",
    "    print(f\"element {i}: {seq[i]}\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 64,
   "metadata": {},
   "outputs": [],
   "source": [
    "total = 0\n",
    "for i in range(100_000):\n",
    "    # % is the modulo operator\n",
    "    if i % 3 == 0 or i % 5 == 0:\n",
    "        total += i\n",
    "print(total)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 65,
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
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