How To Initialize Hashmap In Python

In this tutorial, we will learn how to initialize a Hashmap in Python. A hashmap, also known as a dictionary in Python, is a data structure that stores key-value pairs. Dictionaries are useful when we need to store and retrieve data quickly based on a specific key.

We will walk through the different ways to initialize a dictionary and how to perform basic operations such as adding and removing elements, looping through keys and values, and more.

Step 1: Creating an Empty Dictionary

To create an empty dictionary, simply use curly braces {} or the dict() constructor.

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# Creating an empty dictionary using curly braces
empty_dict = {}
 
# Creating an empty dictionary using the dict() constructor
empty_dict2 = dict()
 
print(empty_dict)
print(empty_dict2)

Output:

{}
{}

Step 2: Initializing a Dictionary with Key-Value Pairs

We can also initialize a dictionary with key-value pairs by placing them inside curly braces {} and separating keys and values with colons.

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# Initializing a dictionary with key-value pairs
person = {
    "name": "John",
    "age": 25,
    "city": "New York"
}
 
print(person)

Output:

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

Step 3: Adding Elements to a Dictionary

We can add new key-value pairs to a dictionary by specifying the key in square brackets [] and assigning a value to it.

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person["country"] = "USA"
print(person)

Output:

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

Step 4: Removing Elements from a Dictionary

We can remove an element from a dictionary by using the del keyword, followed by the key of the element we want to remove.

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del person["city"]
print(person)

Output:

{'name': 'John', 'age': 25, 'country': 'USA'}

Step 5: Looping Through Keys and Values in a Dictionary

We can iterate through the keys and values of a dictionary using a for loop with the items() method, which returns a list of the dictionary’s key-value pairs represented as tuples.

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for key, value in person.items():
    print(f"{key}: {value}")

Output:

name: John
age: 25
country: USA

Step 6: Initializing a Dictionary Using Comprehensions

We can also conveniently create a dictionary using dictionary comprehensions, a concise way to generate dictionaries based on existing iterables.

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# Square numbers dictionary
squares = {x: x * x for x in range(1, 6)}
print(squares)

Output:

{1: 1, 2: 4, 3: 9, 4: 16, 5: 25}

Now that we’ve explored different ways to initialize and work with dictionaries, let’s see the full code example in one place.

Full Code

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# Creating an empty dictionary using curly braces
empty_dict = {}
 
# Creating an empty dictionary using the dict() constructor
empty_dict2 = dict()
 
print(empty_dict)
print(empty_dict2)
 
# Initializing a dictionary with key-value pairs
person = {
    "name": "John",
    "age": 25,
    "city": "New York"
}
 
print(person)
 
# Adding new elements
person["country"] = "USA"
print(person)
 
# Removing an element
del person["city"]
print(person)
 
# Looping through keys and values
for key, value in person.items():
    print(f"{key}: {value}")
 
# Initializing a dictionary using comprehensions
squares = {x: x * x for x in range(1, 6)}
print(squares)

Conclusion

In this tutorial, we learned how to initialize dictionaries (hashmaps) in Python and perform basic operations such as adding, removing, and looping through key-value pairs. Implementing dictionaries in Python makes it easy to create and manage a mapping of keys to associated values, allowing us to improve our code efficiency and readability.