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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "heading",
     "level": 1,
     "metadata": {},
     "source": [
      "Booleans, Tuples, and Dictionaries"
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Booleans"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "A ``boolean`` is one of the simplest Python types, and it can have two values: ``True`` and ``False`` (with uppercase ``T`` and ``F``):"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "a = True\n",
      "b = False"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Booleans can be combined with logical operators to give other booleans:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "True and False"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "True or False"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "(False and (True or False)) or (False and True)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Standard comparison operators can also produce booleans:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "1 == 3"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "1 != 3"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "3 > 2"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "3 <= 3.4"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Exercise 1"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Write an expression that returns ``True`` if ``x`` is strictly greater than 3.4 and smaller or equal to 6.6, or if it is 2, and try changing ``x`` to see if it works:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "x = 3.7\n",
      "\n",
      "# your solution here\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Tuples"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Tuples are, like lists, a type of sequence, but they use round parentheses rather than square brackets:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "t = (1, 2, 3)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "They can contain heterogeneous types like lists:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "t = (1, 2.3, 'spam')"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "and also support item access and slicing like lists:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "t[1]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "t[:2]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "The main difference is that they are **immutable**, like strings:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "t[1] = 2"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "We will not go into the details right now of why this is useful, but you should know that these exist as you may encounter them in examples."
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Dictionaries"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "One of the data types that we have not talked about yet is called *dictionaries* (``dict``). If you think about what a 'real' dictionary is, it is a list of words, and for each word is a definition. Similarly, in Python, we can assign definitions (or 'values'), to words (or 'keywords')."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Dictionaries are defined using curly brackets ``{}``:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "d = {'a':1, 'b':2, 'c':3}"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Items are accessed using square brackets and the 'key':"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "d['a']"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "d['c']"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Values can also be set this way:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "d['r'] = 2.2"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "print(d)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "The keywords don't have to be strings, they can be many (but not all) Python objects:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "e = {}\n",
      "e['a_string'] = 3.3\n",
      "e[3445] = 2.2\n",
      "e[complex(2,1)] = 'value'"
     ],
     "language": "python",
     "metadata": {
      "slideshow": {
       "slide_type": "-"
      }
     },
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "print(e)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "e[3445]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "If you try and access an element that does not exist, you will get a ``KeyError``:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "e[4]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {
      "slideshow": {
       "slide_type": "slide"
      }
     },
     "source": [
      "Also, note that dictionaries do *not* know about order, so there is no 'first' or 'last' element."
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "It is easy to check if a specific key is in a dictionary, using the ``in`` operator:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\"a\" in d"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\"t\" in d"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Note that this also works for lists:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "3 in [1,2,3]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Note, however, that while for dictionaries, ``in`` remains fast when they grow, with lists ``in`` becomes linearly slower as the list grows."
     ]
    },
    {
     "cell_type": "heading",
     "level": 2,
     "metadata": {},
     "source": [
      "Exercise 2"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Try making a dictionary to translate a few English words into German and try using it!"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "\n",
      "# your solution here\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
 ]
}