Python Dictionary

Dictionaries can be used to store key, value pairs in Python for example: {'first_name': 'abhinav', 'last_name': 'upadhay'}
Ordering of the items in the dictionary is not guranteed
They are good for fast search or lookup operations



In [2]:

    
empty_dictionary = {}
print empty_dictionary

{}



In [3]:

    
filled_dictionary = {'first_name': 'abhinav', 'last_name': 'upadhyay'}
print filled_dictionary









    



{'first_name': 'abhinav', 'last_name': 'upadhyay'}



In [4]:

    
food_menu = {}
food_menu['pizza'] = 300
food_menu['sandwich'] = 30
food_menu['tea'] = 10
print food_menu









    



{'tea': 10, 'sandwich': 30, 'pizza': 300}

Notice the ordering of the items in the output above

Values from the dictionary can be read in exactly the same way, they are stored in it.



In [5]:

    
pizza_price = food_menu['pizza']
print pizza_price



In [6]:

    
tea_price = food_menu['tea']
print tea_price

Dictionaries have the pop() method which can be used to pop/remove a value with the given key



In [10]:

    
food_menu.pop('tea')
print food_menu









    



{'sandwich': 30, 'pizza': 300}

Python only allows immutable types to be used as the keys of a dictionary. For example strings, tuples, numbers.

Exercise:

Try to implement an LRU cache using dicts and lists.



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