1 #########################
   2 ## EXAMPLE: returning a tuple
   3 #########################
   4 def quotient_and_remainder(x, y):
   5     q = x // y
   6     r = x % y
   7     return (q, r)
   8     
   9 (quot, rem) = quotient_and_remainder(5,3)
  10 print(quot)
  11 print(rem)
  12 
  13 
  14 #########################
  15 ## EXAMPLE: iterating over tuples
  16 #########################
  17 def get_data(aTuple):
  18     """
  19     aTuple, tuple of tuples (int, string)
  20     Extracts all integers from aTuple and sets 
  21     them as elements in a new tuple. 
  22     Extracts all unique strings from from aTuple 
  23     and sets them as elements in a new tuple.
  24     Returns a tuple of the minimum integer, the
  25     maximum integer, and the number of unique strings
  26     """
  27     nums = ()    # empty tuple
  28     words = ()
  29     for t in aTuple:
  30         # concatenating with a singleton tuple
  31         nums = nums + (t[0],)   
  32         # only add words haven't added before
  33         if t[1] not in words:   
  34             words = words + (t[1],)
  35     min_n = min(nums)
  36     max_n = max(nums)
  37     unique_words = len(words)
  38     return (min_n, max_n, unique_words)
  39 
  40 test = ((1,"a"),(2, "b"),
  41         (1,"a"),(7,"b"))
  42 (a, b, c) = get_data(test)
  43 print("a:",a,"b:",b,"c:",c)
  44 
  45 # apply to any data you want!
  46 tswift = ((2014,"Katy"),
  47           (2014, "Harry"),
  48           (2012,"Jake"), 
  49           (2010,"Taylor"), 
  50           (2008,"Joe"))    
  51 (min_year, max_year, num_people) = get_data(tswift)
  52 print("From", min_year, "to", max_year, \
  53         "Taylor Swift wrote songs about", num_people, "people!")
  54 
  55 #########################
  56 ## EXAMPLE: sum of elements in a list
  57 #########################
  58 def sum_elem_method1(L):
  59   total = 0 
  60   for i in range(len(L)): 
  61       total += L[i] 
  62   return total
  63   
  64 def sum_elem_method2(L):
  65     total = 0 
  66     for i in L: 
  67         total += i 
  68     return total
  69   
  70 print(sum_elem_method1([1,2,3,4]))
  71 print(sum_elem_method2([1,2,3,4]))
  72 
  73 
  74 #########################
  75 ## EXAMPLE: various list operations
  76 ## put print(L) at different locations to see how it gets mutated
  77 #########################
  78 L1 = [2,1,3]
  79 L2 = [4,5,6]
  80 L3 = L1 + L2
  81 L1.extend([0,6])
  82 
  83 L = [2,1,3,6,3,7,0]
  84 L.remove(2)
  85 L.remove(3)
  86 del(L[1])
  87 print(L.pop())
  88 
  89 s = "I<3 cs"
  90 print(list(s))
  91 print(s.split('<'))
  92 L = ['a', 'b', 'c']
  93 print(''.join(L))
  94 print('_'.join(L))
  95 
  96 L=[9,6,0,3]
  97 print(sorted(L))
  98 L.sort()
  99 L.reverse()
 100 
 101 
 102 #########################
 103 ## EXAMPLE: aliasing
 104 #########################
 105 a = 1
 106 b = a
 107 print(a)
 108 print(b)
 109 
 110 warm = ['red', 'yellow', 'orange']
 111 hot = warm
 112 hot.append('pink')
 113 print(hot)
 114 print(warm)
 115 
 116 #########################
 117 ## EXAMPLE: cloning
 118 #########################
 119 cool = ['blue', 'green', 'grey']
 120 chill = cool[:]
 121 chill.append('black')
 122 print(chill)
 123 print(cool)
 124 
 125 #########################
 126 ## EXAMPLE: sorting with/without mutation
 127 #########################
 128 warm = ['red', 'yellow', 'orange']
 129 sortedwarm = warm.sort()
 130 print(warm)
 131 print(sortedwarm)
 132 
 133 cool = ['grey', 'green', 'blue']
 134 sortedcool = sorted(cool)
 135 print(cool)
 136 print(sortedcool)
 137 
 138 #########################
 139 ## EXAMPLE: lists of lists of lists...
 140 #########################
 141 warm = ['yellow', 'orange']
 142 hot = ['red']
 143 brightcolors = [warm]
 144 brightcolors.append(hot)
 145 print(brightcolors)
 146 hot.append('pink')
 147 print(hot)
 148 print(brightcolors)
 149 
 150 
 151 ###############################
 152 ## EXAMPLE: mutating a list while iterating over it
 153 ###############################
 154 def remove_dups(L1, L2):
 155     for e in L1:
 156         if e in L2:
 157             L1.remove(e)
 158       
 159 def remove_dups_new(L1, L2):
 160     L1_copy = L1[:]
 161     for e in L1_copy:
 162         if e in L2:
 163             L1.remove(e)
 164 
 165 L1 = [1, 2, 3, 4]
 166 L2 = [1, 2, 5, 6]
 167 remove_dups(L1, L2)
 168 print(L1, L2)
 169 
 170 L1 = [1, 2, 3, 4]
 171 L2 = [1, 2, 5, 6]
 172 remove_dups_new(L1, L2)
 173 print(L1, L2)
 174 
 175 ###############################
 176 ## EXERCISE: Test yourself by predicting what the output is and 
 177 ##           what gets mutated then check with the Python Tutor
 178 ###############################
 179 cool = ['blue', 'green']
 180 warm = ['red', 'yellow', 'orange']
 181 print(cool)
 182 print(warm)
 183 
 184 colors1 = [cool]
 185 print(colors1)
 186 colors1.append(warm)
 187 print('colors1 = ', colors1)
 188 
 189 colors2 = [['blue', 'green'],
 190           ['red', 'yellow', 'orange']]
 191 print('colors2 =', colors2)
 192 
 193 warm.remove('red') 
 194 print('colors1 = ', colors1)
 195 print('colors2 =', colors2)
 196 
 197 for e in colors1:
 198     print('e =', e)
 199 
 200 for e in colors1:
 201     if type(e) == list:
 202         for e1 in e:
 203             print(e1)
 204     else:
 205         print(e)
 206 
 207 flat = cool + warm
 208 print('flat =', flat)
 209 
 210 print(flat.sort())
 211 print('flat =', flat)
 212 
 213 new_flat = sorted(flat, reverse = True)
 214 print('flat =', flat)
 215 print('new_flat =', new_flat)
 216 
 217 cool[1] = 'black'
 218 print(cool)
 219 print(colors1)