Initialize a Dictionary with Empty List in Python

This tutorial will discuss about unique ways to initialize a dictionary with empty list in Python.

Table Of Contents

Using Dictionary Comprehension

Dictionary in Python stores the data as a key value pairs. Now suppose you want to store an empty list as a value for each key in the dictionar.

So, we can do that using two ways, first one is a dictionary comprehension. Where, we will iterate over the sequence of keys and for each key we will assign the value as empty list in the dictionary comprehension. It will return a dictionary containing keys from the list but each value will be the empty list.

Let’s see the complete example,

listOfKeys = ['Ritika', 'Atharv', 'Smriti', 'Mathew', 'John']

# Create a dictionary with empty list as values
dictObj = {key: [] for key in listOfKeys}

print(dictObj)

Output

{'Ritika': [], 'Atharv': [], 'Smriti': [], 'Mathew': [], 'John': []}

Using fromkeys() method

To initialise a dictionary with keys and an empty list as the default value, we can use the fromkeys() method from the dictionary. We will pass the list of keys as first argument and an empty list as the second argument in the fromkeys() method.

It will initialise, and return a dictionary object, where the items from the list keys will be the keys in the key-value pairs, and each key will have the empty list as default value.

Let’s see the complete example,

listOfKeys = ['Ritika', 'Atharv', 'Smriti', 'Mathew', 'John']

# Create a dictionary with empty list as values
dictObj = dict.fromkeys(listOfKeys, [])

print(dictObj)

Output

{'Ritika': [], 'Atharv': [], 'Smriti': [], 'Mathew': [], 'John': []}

Summary

We learned about two different ways to initialise a dictionary with an empty list in Python.