The efficient and Pythonic way to create an empty dictionary is using the “{}” literal notation.

There is a dictionary object in memory, but it does not have data (key-value pairs). That does not mean it is None because None means nothing in memory, while an empty dictionary has an object.

empty_dict = {}

print(empty_dict)
# Output: {}

print(type(empty_dict))
# Output: <class 'dict'>

The “{}” literal is the fastest approach because Python’s bytecode directly interprets it, and it does not require a function call, which reduces the overhead. For simplicity and readability, this approach is more appropriate.

Using dict() constructor

Another way is to assign the dict() constructor without any arguments to a variable, which will result in an empty dictionary.

empty_dict = dict()

print(empty_dict)
# Output: {}

print(type(empty_dict))
# Output: <class 'dict'>

It is slower than the literal ({}) approach because it requires a function call.

Checking if a dictionary is empty

The most optimal way to check if a dictionary is empty is to use an implicit boolean check using the “not” operator with an “if statement”.

Dictionaries are inherently truthy if they contain at least one key-value pair and falsy if empty; therefore, this approach is efficient. Since empty mechanisms are falsy, not empty mechanisms become truthy.

empty_dict = {}

if not empty_dict:
    print("The dictionary is empty")
else:
    print("The dictionary is not empty")

# Output: The dictionary is empty

If a dictionary contains a single element, if condition won’t be executed:

dict = {'name': 'Krunal'}

if not dict:
    print("The dictionary is empty")
else:
    print("The dictionary is not empty")

# Output: The dictionary is not empty

The time complexity is O(1), which is why it’s the fastest.

You can also use a simple if-else condition if you don’t want to use the not operator:

empty_dict = {}

if empty_dict:
    print("The dictionary is not empty")
    
else:
    print("The dictionary is empty")

# Output: The dictionary is empty

Using explicit length checking

An empty dictionary has a length of zero, and using the len() function, we can compare the dictionary’s length to zero to determine whether it is empty or not.

empty_dict = {}

if len(empty_dict) == 0:
    print("The dictionary is empty")
else:
    print("The dictionary is not empty")

# Output: The dictionary is empty

It is not as fast and efficient as an explicit Boolean check because here, we need to call a function, which adds a slight overhead.

Comparing a dictionary with {}

There is a third way, which involves directly comparing an empty dictionary with “{}”. However, this approach is not advisable since “{}” creates a new dictionary for comparison, consuming both memory and time. 

It has O(1) efficiency for checking an empty dictionary, but is inefficient for large dicts.

empty_dict = {}

if empty_dict == {}:
    print("The dictionary is empty")
else:
    print("The dictionary is not empty")

# Output: The dictionary is empty

If possible, please avoid this approach entirely.

That’s all!