Python | Check if dictionary is empty

Sometimes, we need to check if a particular dictionary is empty or not. In the web development domain in which we sometimes need to test for results of a particular query or check whether we have any key to add info into a database. Let’s discuss certain ways in which this task can be performed in Python. 

Check if a Dictionary is Empty using bool()

The bool function can be used to perform this particular task. As the name suggests it performs the task of converting an object to a boolean value, but here, passing an empty string returns a False, as a failure to convert something that is empty. 

Python3

# initializing empty dictionary
test_dict = {}

# printing original dictionary
print("The original dictionary : " + str(test_dict))

# using bool()
# Check if dictionary is empty
res = not bool(test_dict)

# print result
print("Is dictionary empty ? : " + str(res))

Output :

The original dictionary : {}
Is dictionary empty ? : True

Check if a Dictionary is Empty using not operator

This task can also be performed using the not operator that checks for a dictionary existence, this evaluates to True if any key in the dictionary is not found. 

Python3

# initializing empty dictionary
test_dict = {}

# printing original dictionary
print("The original dictionary : " + str(test_dict))

# using not operator
# Check if dictionary is empty
res = not test_dict

# print result
print("Is dictionary empty ? : " + str(res))

Output:

The original dictionary : {}
Is dictionary empty ? : True

Check if a Dictionary is Empty using len()

Here, we are using the Python len() to check if the dictionary is empty or not.

Python3

# initializing empty dictionary
test_dict = {}

# printing original dictionary
print("The original dictionary : " + str(test_dict))

# Check if dictionary is empty using len
res = len(myDict) == 0

# print result
print("Is dictionary empty ? : " + str(res))

Output:

The original dictionary : {}
Is dictionary empty ? : True

Check if a Dictionary is Empty using the Equality Operator

Here, we are comparing the dictionary with values with an empty dictionary to check if the dictionary is empty or not.

Python3

# initializing empty dictionary
myDict = {1: 'Hello', 2: 'World' }
test_dict = {}

# printing original dictionary
print("The original dictionary : " + str(myDict))

# using operator
# Check if dictionary is empty
res = test_dict == myDict

# print result
print("Is dictionary empty ? : " + str(res))

Output

The original dictionary : {1: 'Hello', 2: 'World'}
Is dictionary empty ? : False

Check if a Dictionary is Empty using the Using the not operator with the __len__() method:

This approach is similar to the previous one, but it uses the __len__() method instead of the len() function to get the length of the dictionary.

Python3

# Initialize a dictionary with some key-value pairs
myDict = {1: 'Hello', 2: 'World' }

# Print the original dictionary
print("The original dictionary : " + str(myDict))

# Check if the dictionary is empty using the equality operator
res = myDict.__len__()==0

# Print the result
print("Is dictionary empty ? : " + str(res))
#This code is contributed by Edula Vinay Kumar Reddy

Output

The original dictionary : {1: 'Hello', 2: 'World'}
Is dictionary empty ? : False

Time complexity: O(1)

Auxiliary Space:  O(1)