0-intro-python.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Write in the input space, click `Shift-Enter` or click on the `Play` button to execute."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "292"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "(3 + 1 + 12) ** 2 + 2 * 18"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Give a title to the notebook by clicking on `Untitled` on the very top of the page, better not to use spaces because it will be also used for the filename"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Save the notebook with the `Diskette` button, check dashboard"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Integer division gives integer result with truncation in Python 2, float result in Python 3:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "1"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "5/3"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "1/3"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Quotes for strings"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello world\n"
     ]
    }
   ],
   "source": [
    "print(\"Hello world\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello world\n"
     ]
    }
   ],
   "source": [
    "print('Hello world')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Look for differences"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'Hello world'"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "\"Hello world\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello world\n"
     ]
    }
   ],
   "source": [
    "print(\"Hello world\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Multiple lines in a cell"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "7"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "1 + 2\n",
    "3 + 4"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "3\n",
      "7\n"
     ]
    }
   ],
   "source": [
    "print(1 + 2)\n",
    "print(3 + 4)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "This is \n",
      "a multiline\n",
      "Hello world\n"
     ]
    }
   ],
   "source": [
    "print(\"\"\"This is \n",
    "a multiline\n",
    "Hello world\"\"\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Functions and help"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "2"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "abs(-2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Write a function name followed by `?` to open the help for that function.\n",
    "\n",
    "type in a cell and execute: `abs?`"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Heading 1"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Heading 2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Structured plain text format, it looks a lot like writing text **emails**,\n",
    "you can do lists:\n",
    "\n",
    "* like\n",
    "* this\n",
    "\n",
    "write links like <http://google.com>, or [hyperlinking words](http://www.google.com)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "go to <http://markdowntutorial.com/> to learn more"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "$b_n=\\frac{1}{\\pi}\\int\\limits_{-\\pi}^{\\pi}f(x)\\sin nx\\,\\mathrm{d}x=\\\\\n",
    "=\\frac{1}{\\pi}\\int\\limits_{-\\pi}^{\\pi}x^2\\sin nx\\,\\mathrm{d}x$"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Variables"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {
    "cell_tags": [],
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "weight_kg = 55"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "cell_tags": []
   },
   "source": [
    "Once a variable has a value, we can print it:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {
    "cell_tags": [],
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "55\n"
     ]
    }
   ],
   "source": [
    "print(weight_kg)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "cell_tags": []
   },
   "source": [
    "and do arithmetic with it:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {
    "cell_tags": [],
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "weight in pounds:\n",
      "121.0\n"
     ]
    }
   ],
   "source": [
    "print('weight in pounds:')\n",
    "print(2.2 * weight_kg)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "cell_tags": []
   },
   "source": [
    "We can also change a variable's value by assigning it a new one:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {
    "cell_tags": [],
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "weight in kilograms is now:\n",
      "57.5\n"
     ]
    }
   ],
   "source": [
    "weight_kg = 57.5\n",
    "print('weight in kilograms is now:')\n",
    "print(weight_kg)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "cell_tags": []
   },
   "source": [
    "As the example above shows,\n",
    "we can print several things at once by separating them with commas.\n",
    "\n",
    "If we imagine the variable as a sticky note with a name written on it,\n",
    "assignment is like putting the sticky note on a particular value:"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "cell_tags": []
   },
   "source": [
    "<img src=\"files/img/python-sticky-note-variables-01.svg\" alt=\"Variables as Sticky Notes\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "cell_tags": []
   },
   "source": [
    "This means that assigning a value to one variable does *not* change the values of other variables.\n",
    "For example,\n",
    "let's store the subject's weight in pounds in a variable:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {
    "cell_tags": [],
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "weight in kilograms:\n",
      "57.5\n",
      "and in pounds:\n",
      "126.5\n"
     ]
    }
   ],
   "source": [
    "weight_lb = 2.2 * weight_kg\n",
    "print('weight in kilograms:')\n",
    "print(weight_kg)\n",
    "print('and in pounds:')\n",
    "print(weight_lb)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"files/img/python-sticky-note-variables-02.svg\" alt=\"Creating Another Variable\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "cell_tags": []
   },
   "source": [
    "and then change `weight_kg`:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "cell_tags": [],
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "weight in kilograms is now:\n",
      "100.0\n",
      "and weight in pounds is still:\n",
      "126.5\n"
     ]
    }
   ],
   "source": [
    "weight_kg = 100.0\n",
    "print('weight in kilograms is now:')\n",
    "print(weight_kg)\n",
    "print('and weight in pounds is still:')\n",
    "print(weight_lb)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<img src=\"files/img/python-sticky-note-variables-03.svg\" alt=\"Updating a Variable\" />"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "cell_tags": []
   },
   "source": [
    "Since `weight_lb` doesn't \"remember\" where its value came from,\n",
    "it isn't automatically updated when `weight_kg` changes.\n",
    "This is different from the way spreadsheets work."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Challenge"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "x = 5\n",
    "y = x\n",
    "x = x**2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "How much is `x`? how much is `y`?"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Comments"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 19,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "220.0\n"
     ]
    }
   ],
   "source": [
    "weight_kg = 100.0 # assigning weight\n",
    "# now convert to pounds\n",
    "print(2.2 * weight_kg)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Strings slicing"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 20,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "my_string = \"Hello world\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hello world\n"
     ]
    }
   ],
   "source": [
    "print(my_string)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python by convention starts indexing from `0`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hel\n"
     ]
    }
   ],
   "source": [
    "print(my_string[0:3])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Hel\n"
     ]
    }
   ],
   "source": [
    "print(my_string[:3])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Python uses intervals open on the right: $ \\left[7, 9\\right[ $"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "or\n"
     ]
    }
   ],
   "source": [
    "print(my_string[7:9])"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Challenge"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "What happens if you print:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "\n"
     ]
    }
   ],
   "source": [
    "print(my_string[4:4])"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.6.5"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}