07-Tuples&Sets

Tuple

• Ordered collection of items (item1, item2)
• it is immutable and cannot be changed
• we can also have nested tuples

WHY USE THEM?

• they are faster if you don't mind immutability

• makes code safer, value doesn't get changed

• can act as valid keys in dict, unlike lists

• some methods return tuples

• An example for using tuple in a real case can be days of a week

  days = tuple(monday, tuesday, wednesday, thursday, friday, saturday, sunday)
  
  # access data with index
  print(days[0]) # monday

TUPLE METHODS

• count(item) - returns how many times the specified item is in tuple
• index(item) - returns the index of the specified item's first instance

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Sets

• just like mathematical sets, created by {}

• cannot have duplicate values

• are unordered, hence can't be access by index

  # defining sets
  s = {1, 2, 3}
  
  s2 = set({4, 5, 6})

WHY USE THEM?

Suppose I have 100 people coming from a lot of cities and we want to find the unique cities. We can create a set out of the list of cities.

projects = ['java', 'HTML', 'python', 'java', 'css', 'python']

# finding unique stack
stack = set(projects)

SET METHODS

• add(item) - adds item to the set; ignores if item is already there
• remove(item) - removes item; throws error if item isn't there
• discard(item) - removes item; doesn't throw error if item isn't there
• copy() - creates a copy of the set
• clear() - removes all the items from the set
• There are many mathematical methods with sets like union and intersection

Set Comprehension

• same stuff as we have for list and dict comprehension

• useful when we convert other data types into set to get unique instances

  s = {x **2 for x in range(5)}
  print(s) # {0, 1, 4, 9, 16}
  
  print({letter for letter in "hello"}) # {'h', 'o', 'l', 'e'}