How to add values to dictionary in Python

In this article, we will learn what are the different ways to add values in a dictionary in Python. 

Assign values using unique keys

After defining a dictionary we can index through it using a key and assign a value to it to make a key-value pair.

Python3

veg_dict = {}
veg_dict[0] = 'Carrot'
veg_dict[1] = 'Raddish'
veg_dict[2] = 'Brinjal'
veg_dict[3] = 'Potato'

print(veg_dict)

Output:

{0: ‘Carrot’, 1: ‘Raddish’, 2: ‘Brinjal’, 3: ‘Potato’}

But what if a key already exists in it?

Python3

veg_dict[0] = 'Tomato'
print(veg_dict)

Output:

{0: ‘Tomato’, 1: ‘Raddish’, 2: ‘Brinjal’, 3: ‘Potato’}

We can observe that the value corresponding to key 0 has been updated to ‘Tomato’ from ‘Carrot’.

Merging two dictionaries using update()

We can merge two dictionaries by using the update() function.

Python3

veg_dict = {0: 'Carrot', 1: 'Raddish',
            2: 'Brinjal', 3: 'Potato'}

veg_dict.update({4: 'Tomato', 5: 'Spinach'})
print(veg_dict)

Output:

{0: ‘Carrot’, 1: ‘Raddish’, 2: ‘Brinjal’, 3: ‘Potato’, 4: ‘Tomato’, 5: ‘Spinach’}

Add values to dictionary Using two lists of the same length

This method is used if we have two lists and we want to convert them into a dictionary with one being key and the other one as corresponding values.

Python3

roll_no = [10, 20, 30, 40, 50]
names = ['Ramesh', 'Mahesh', 'Kamlesh',
         'Suresh', 'Dinesh']

students = dict(zip(roll_no, names))
print(students)

Output:

{10: ‘Ramesh’, 20: ‘Mahesh’, 30: ‘Kamlesh’, 40: ‘Suresh’, 50: ‘Dinesh’}

Converting a list to the dictionary

This method is used to convert a python list into a python dictionary with indexes as keys.

Python3

vegetables = ['Carrot', 'Raddish',
              'Brinjal', 'Potato']

veg_dict = dict(enumerate(vegetables))
print(veg_dict)

Output:

{0: ‘Carrot’, 1: ‘Raddish’, 2: ‘Brinjal’, 3: ‘Potato’}

There are other methods as well to add values to a dictionary but the above-shown methods are some of the most commonly used ones and highly efficient as well.

Add values to dictionary Using the merge( | ) operator

By using the merge operator we can combine two dictionaries.

Python3

veg1 = {0: 'Carrot', 1: 'Raddish'}
veg2 = {2: 'Brinjal', 3: 'Potato'}

veg_dict = (veg1 | veg2)
print(veg_dict)

Output:

{0: ‘Carrot’, 1: ‘Raddish’, 2: ‘Brinjal’, 3: ‘Potato’}

Add values to dictionary Using the in-place merge( |= ) operator.

By using the in place merge operator we can combine two dictionaries. In in place operator, all elements of one dictionary are added in the other but while using merge original state of the dictionaries remains the same and a new one is created.

Python3

veg1 = {0:'Carrot', 1:'Raddish'}
veg2 = {2:'Brinjal', 3:'Potato'}

veg1 |= veg2
print(veg1)

Output:

{0: ‘Carrot’, 1: ‘Raddish’, 2: ‘Brinjal’, 3: ‘Potato’}

Note: Methods 4 and 5 work in only Python 3.9+ versions.