Python Data Structures

Tuples

• Tuples are an ordered sequence
• Here is a Tuple “Ratings”
• Tuples are written as comma-separated elements within parentheses
• Tuples concatenation is possible
• Tuple slicing is also possible
• Tuples are immutable
• If one want to manipulate tuples, they have to create a new tuple with the desired values

• Tuples nesting (tuple containing another tuple) is also possible

  Ratings = (10, 9, 6, 5, 10, 8, 9, 6, 2)
  

  

  

  

  

  

  

Lists

• Lists are also ordered in sequence

• Here is a List “L”

  L = ["Michael Jackson", 10.1, 1982]
  

• A List is represented with square brackets
• List is mutable
• List can nest other lists and tuples
• We can combine lists
• List can be extended with extend() method

• append.() adds only one element to the List, if we append L.append([1,2,3,4]), the List “L” will be:

  L = ["Michael Jackson", 10.1, 1982,[1,2,3,4]]
  

• The method split() can convert the string into the List

  "Hello, World!".split()
  

• The split() can be used with a delimiter we would like to split on as an argument

  "A,B,C,D".split(",")
  

• Multiple names referring to the same object is known as aliasing

• We can clone the list, where both lists will be of their independent copies
• So changing List “A”, will not change List “B”

Dictionaries

• Dictionaries are denoted with curly Brackets {}
• The keys have to be immutable and unique
• The values can be immutable, mutable and duplicates
• Each key and value pair is separated by a comma

Sets

• Sets are a type of collection
  • This means that like lists and tuples you can input different python types
• Unlike lists and tuples they are unordered
  • This means sets don’t record element position
• Sets only have unique elements
  • This means there is only one of a particular element in a set

Sets: Creating a Set

• You can convert a list into set

  List = ['foo']
  set(List)
  

• To add elements to the set, set.add('foo')
• To remove an element, set.remove(‘foo’)

• To check if an element is present in the set:

  'foo' in set
  True/False
  

Sets: Mathematical Expression

• To find the intersection of the sets elements present in the both sets), set1 & set2 or set1.intersection(set2)

• Union of the sets, contain elements of both the sets combined, set1.union(set2)

• To find the difference of sets:

  #set1 difference from set2
  set1.difference(set2)
  #set2 difference from set 1
  set2.difference(set1)
  

• To find is a set is a subset/superset (have all the elements of other set), `set1.issubset/issuperset(set2)