Python Dictionary Comprehension

Python dictionary data type is used to store data in key:value pairs. It can be created in two ways first is by placing the comma-separated items inside curly braces and the second is to create using dict() function.

For example –

users={1:'Ankit', 2:'Sumit', 3:'John', 4:'Vinay'}

Python dictionary comprehension provides a shorter syntax to create dictionaries. In this article, you will learn Python dictionary comprehension and how to use it.

How to create a dictionary using dictionary comprehension

The syntax for creating a Python dictionary using dictionary comprehension is given below.

dict_var={key:value for (key, value) in iterable}

Where dict_var is the dictionary variable, the key: value pairs will get added to dict_var.

Example of Python dictionary created using dictionary comprehension

In our example, we will create a dictionary whose keys range from 0 to 5  and whose values are the cube of corresponding keys. First, we will create this with the usual method that we use later we create using dictionary comprehension.

cube_dict = dict()
for num in range(0,6):
     cube_dict[num] = num**3
print(cube_dict)

How to Use dictionary comprehension in Python

You can write the same code in a few lines by using dictionary comprehension. Now see the code below.

cube_dict = {num:num**3 for num in range(0,6)}
print(cube_dict)

You can see the output in the given image –

Use of Python conditional statements in dictionary comprehension

You can use any python conditional statements in dictionary comprehension to modify the output on the basis of a condition. We will understand this with the help of an example.

We will create a dictionary with keys even numbers ranging from 1 to 15 and whose values are cubes of corresponding keys.

cube_dict = {num: num**3 for num in range(1,15) if num%2==0}
print(cube_dict)

You can see the output of this in the given image –

Python nested dictionary

A dictionary inside a dictionary is known as a nested dictionary. An example of a nested dictionary is given below-

users={ 1:{'name':'Sumit', 'age'=24},
        2:{'name':'Ajay' 'age'=25},
        3:{'name':'Vinay' 'age'=20}
      }

The syntax for creating Python nested dictionary using dictionary comprehension is given below:

dict_var={outer_k:{inner_k:inner_v for inner_k,inner_v in outer_v.items()} for outer_k, outer_v in outer_dict.items()}

Where inner_k and inner_v are the key and value of the inner dictionary similarly outer_k and outer_v are the key and value of the outer dictionary.

Conclusion

Python dictionary comprehension provides a shorter syntax to create dictionaries so you can write the same code in fewer lines.

Now you can leave your query in the comments below.