How to Initialize Dictionary in Python

In Python dictionary, each key is unique and we can store different data types as values. The simplest and most efficient method to initialize a dictionary is using curly braces {}. This is the easiest and most common way to create a dictionary.

We can use curly braces '{} ' and separate the keys and values with : colon. Each key-value pair is separated by a comma.

a = {"name": "John", "age": 25, "city": "New York"}

# Print the dictionary
print(a)

{'name': 'John', 'age': 25, 'city': 'New York'}

Other methods we can use to initialise a dictionary are:

Using dict() Constructor

Another way to create a dictionary is by using the dict() constructor. This method is useful when you want to create a dictionary from a list of tuples or from keyword arguments.

a = dict(name="Alice", age=30, city="Los Angeles")

# Print the dictionary
print(a)

{'name': 'Alice', 'age': 30, 'city': 'Los Angeles'}

We can also use list of key-value tuples to initialize a dictionary.

a = dict([("name", "Bob"), ("age", 35), ("city", "Chicago")])

# Print the dictionary
print(a)

{'name': 'Bob', 'age': 35, 'city': 'Chicago'}

Using a Dictionary Comprehension

Dictionary comprehension is a more advanced method to create a dictionary, but it's still quite simple and powerful. It lets us create a dictionary by iterating over a sequence, such as a list or range.

a = {x: x**2 for x in range(5)}

# Print the dictionary
print(a)

{0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

Using fromkeys() Method

If we want to create a dictionary with predefined keys and the same value for all keys, we can use the fromkeys() method.

a = dict.fromkeys(["name", "age", "city"], "Unknown")

# Print the dictionary
print(a)

{'name': 'Unknown', 'age': 'Unknown', 'city': 'Unknown'}