• Data Structures.
  • A set is declared using curly brackets. 
    mySet = {'a', 'b', 'c'}
mySet
  • You can also define it by passing any iterable object of the constructor of the set class. 
    mySet = set(['a', 'b', 'c'])
  • If you use a Tuple, you receive the same set: 
    mySet = set(('a', 'b', 'c'))
  • A common pattern in programming is duplicate removal from a list.
  • You can convert a list to a set and then back again, sets can only contain unique values. 
    myList = ['a', 'b', 'b', 'c', 'c']
myList = list(set(myList))
myList
  • The above will then remove duplicates and show ['a', 'b', 'c']
  • Properties of Sets:
    • The order does not matter.
    • Declared with curly brackets.
    • All elements are unique.
    • Sets are randomised.
    • The order of elements in the list, may not be the same coming back out.
      • Because of this, you can’t fetch elemets by index. 
        mySet[0]
  • The above will output an error.
  • In Python, object is subscriptable, if it contains items that can be accessed by an Index.
  • It contains ordered, accessible sub elements.
  • For example: 
    number = 1
1[0]
  • You would receive an output for the above message.
    • It doesn’t make sense to get the first element in a big random pile.
  • You can add elements to a set, for example:
    • mySet.add('d')
      • The add function tosses the element onto the pile.
      • Outputs: {'a', 'b', 'c', 'd'}
  • Like with lists, you can use the membership operator to return boolean values.
    • 'a' in mySet
      • Outputs to True, because we have a.
    • 'z' in mySet:
      • False
  • Can use the length function as well, for example len(mySet) = 4
  • Set dose have a pop function and you pop the element off the set. 
    while len(mySet):
       print(mySet.pop())
  • Will output and remove the following: 
    a
b
c
d
  • If you want to remove a specific element, you can do that with: 
    mySet.discard('a')
  • It will not throw an error, even though mySet is empty.
  • Will then output {'b', 'c'}
  • Tuples
    • Very much like Lists - have an order and declared with parenthesis.
    • Ordered and subscriptable.
    • Cannot be modified. 
      myTuple = ('a', 'b', 'c')
myTuple
  • Will output: 
    ('a', 'b', 'c')
  • To get the first element of the Tuple:
    • myTuple[0] = a.
  • If you try to assign a Tuple, such as myTuple[0] = 'd', this will throw an error.
  • Why Use Tuples?
    • More efficient than lists.
    • They don’t grow or change.
    • Store compactly in memory.
    • Often used by default.
  • Write a Python function with multiple values, separated by commas. 
    def returnMultipleValues():
# The syntax below is preferred
  return 1,2,3
# Call it and put whatever it is returning into the type function:
type(returnMultipleValues())
  • This will output –> tuple
  • Can also use a Tuple as myTuple = 1,2,3 (without any parentheses).
    • Best to add parentheses around any tuple.
  • The below is called unpacking values:
  • Can set multiple values in a row, for example –> a, b, c = returnMultipleValues() 
    print(a)
print(b)
print(c)
  • Shows output as: 
    1
2
3

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