Python Set and Dictionary

What is Set?

• A Set is an unordered collection data type that is iterable, mutable, and has no duplicate elements. A set is a collection that is both unorderedand unindexed. Sets are written with curly brackets.

How to create Set?

• myset = {“revin”, “reviving”, 54, 54.36}
• print(myset)
• x = set([1,2,3,4])
• print(x,type(x))

Empty Set

• # Empty set using set() function  
• myset= set()
• print(type(myset))

Read and Access

• In set we can’t access using index or key only we can loop to get the elements or items of set.
• myset = {“revin”, “reviving”, 54, 54.36}
• for var in myset:
• print(myset)
• print(myset) #complete accesss

Add or Change

• We cannot change its items, but you can add new items.We can add new items with add() & update() method

Add() method  to add one item to a set use the add() method.

• myset.add(“hello world”)
  print(myset)

Update method() To add items from another set into the current set, use the update() method.

• myset1 = {“revin”, “reviving”, 54, 54.36}
• myset2 = {1, 2}
• myset1.update(myset2)

Remove : To remove an item in a set, use following methods:

• remove
• discared
• pop
• clear
• del

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What is Dictionary?

• A dictionary consists of a collection of key-value pairs.Dictionary items are unordered, changeable, and does not allow duplicates keys. Dictionaries cannot have two items with the same key.

How to create Dictionary?

• To create a dictionary declare key-value pairs enclosing a comma-separated in curly braces ({})
• A colon (:) separates each key from its associated value.

Creating a Dictionary

• mydict= {1: ‘Reviving’, ‘a’: ‘India’, 34.5: ‘Revin’}
• print(mydict)

Creating an empty Dictionary

• mydict = {}
• print(“Empty Dictionary: “)
• print(mydict)

ACCESS DICTIONARY ITEMS

• He items of a dictionary can be accessed by referring to its key name, inside square brackets.
• mydict[1]  
• Get() method is also used to get the value of existing key in dictionary
• x = mydict.get(1)
• If we use the square brackets [], KeyErroris raised in case a key is not found in the dictionary. On the other hand, the get() method returns None if the key is not found.

ACCESS ALL THE KEYS

• The keys() method will return a list of all the keys in the dictionary.
• mydict.keys()

ACCESS ALL THE VALUES

• The values() method will return a list of all the values in the dictionary.
• mydict.values()

KEY,VALUE BOTH ACCESS

• The items() method will return each item in a dictionary, as tuples in a list.
• mydict.items()

How to update Dictionary?

• The value of a specific item or key can be changed by referring to its key name.
• mydict[1] = ’2021’
• If the key will not exist in the dictionary , then it will add the key value pair rather than update.

UPDATE : The update() method will update the dictionary with the items from the given argument.

• mydict.update({1: 58})

REMOVE DICT ITEMS

• pop – method removes the item with the specified key name
• popitem():  method removes the last inserted item.
• Del –  keyword removes the item with the specified key name
• Clear : This method removes all the elements from a dict