Create a Dictionary in Python

You can create a dictionary using curly braces {} or the dict() constructor.

1. Using curly braces {}

You can use {} to create a dictionary with key-value pairs separated by commas.

For example:

person = {"name": "James", "age": 35, "city": "New York"}

You can also write the above code in multiple lines for better readability, like this:

person = {
    "name": "James",
    "age": 35,
    "city": "New York"
}

You can also create an empty dictionary and add key-value pairs later.

# Create an empty dictionary
person = {}

# Add key-value pairs later
person["name"] = "James"
person["age"] = 35
person["city"] = "New York"

# Print the dictionary
print(person) # Output: {'name': 'James', 'age': 35, 'city': 'New York'}

2. Using dict() constructor

To create a dictionary using the dict() constructor, you can pass key-value pairs as arguments.

For example:

person = dict(name="James", age=35, city="New York")

You can also create an empty dictionary using the dict() constructor and add key-value pairs later.

# Create an emtpy dictionary
person = dict()

# Add key-value pairs later
person["name"] = "James"
person["age"] = 35
person["city"] = "New York"

# Print the dictionary
print(person) # Output: {'name': 'James', 'age': 35, 'city': 'New York'}

Creating a dictionary from an iterable of key-value pairs

You can use the dict() constructor to create a dictionary from an iterable of key-value pairs such as a list of tuples.

For example:

# List of tuples
key_value_pairs = [('a', 1), ('b', 2), ('c', 3)]

# Creating a dictionary from the iterable
my_dict = dict(key_value_pairs)

print(my_dict) # Output: {'a': 1, 'b': 2, 'c': 3}

When to use:

(1) Use {} when:

• You are manually defining the dictionary with known key-value pairs.
• It is slightly faster than the dict() constructor because it doesn’t involve a function call.

(2) Use dict() constructor when:

• You need to create a dictionary dynamically.
• You need to create a dictionary from an iterable of key-value pairs (e.g., a list of tuples).