Dictionaries in Python

Dictionaries hold key-value pairs which are known as items.

SYNTAX :

dictionary_name = { key_1 : value_1, key_N : value_N}

Empty dictionary

dictionary_name = {}

To access items from the dictionary

dictionary_name[ key ]

Example :

Students = {'Akshat' : 100 , 'Raju' :80 , 'Naresh':90}
Akshat_score = Students['Akshat']
print('Score of akshat is {}'.format(Akshat_score))

OUTPUT : Score of akshat is 100

To Replace a value in Dictionary

Students = {'Akshat' : 100 , 'Raju' :80 , 'Naresh':90}
Students['Akshat'] = 99
Akshat_score = Students['Akshat']
print('Score of akshat is {}'.format(Akshat_score))

OUTPUT : Score of akshat is 99

Add new item in dictionary

Students = {'Akshat' : 100 , 'Raju' :80 , 'Naresh':90}
Students['Pareek'] = 80
print(Students)

OUTPUT : {'Pareek': 80, 'Akshat': 100, 'Naresh': 90, 'Raju': 80}  

Remove items from dictionary: use del keyword

Students = {'Akshat' : 100 , 'Raju' :80 , 'Naresh':90}
del Students['Raju']
print(Students)

OUTPUT : {'Naresh': 90, 'Akshat': 100}

Accessing multiple values for a single value using for loop

Students = {'Akshat' : [100 ,89,90], 'Raju' :80 , 'Naresh':90}
for num in Students['Akshat'] :
    print('Marks are {}'.format(num))


OUTPUT :
Marks are 100                                                                                                                                            
Marks are 89                                                                                                                                             
Marks are 90

How to use keys() and values() functions ? Check below example

Students = {'Akshat' : [100 ,89,90], 'Raju' :80 , 'Naresh':90}

if 'Akshat' in Students.keys() :
    print(Students['Akshat'][0])
else:
    print('not found')

OUTPUT : 100

Students = {'Akshat' : [100,89,90], 'Raju' :80 , 'Naresh':90}
print (80 in Students.values())

OUTPUT : True

Looping in Dictionaries

website = {
    'Technoname':'Best website',
    'DevelopedBy' : 'Akshat Jain'
}
for num in website :
    print('{0} {1}'.format(num, website[num]))

OUTPUT :
Technoname Best website                                                                                                                                  
DevelopedBy Akshat Jain