A Quick Note on Python Dictionaries

Dictionaries are used to store data values in key:value pairs. A dictionary is a collection which is ordered (starting from Python 3.7), changeable, and does not allow duplicate keys.

Creating Dictionaries

Dictionaries are written with curly brackets, and have keys and values.

# A dictionary of a person's information
person = {
    "first_name": "Shivraj",
    "last_name": "Badu",
    "age": 30
}

Accessing Items

You can access the items of a dictionary by referring to its key name, inside square brackets.

print(person["first_name"])  # 'Shivraj'

There is also a method called get() that will give you the same result:

print(person.get("age"))  # 30

The difference is that get() will return None if the key does not exist, while using square brackets will raise a KeyError.

Dictionary Methods

Python has a set of built-in methods that you can use on dictionaries.

• keys(): Returns a view object that displays a list of all the keys in the dictionary.
• values(): Returns a view object that displays a list of all the values in the dictionary.
• items(): Returns a view object that displays a list of a given dictionary’s key-value tuple pair.

print(person.keys())    # dict_keys(['first_name', 'last_name', 'age'])
print(person.values())  # dict_values(['Shivraj', 'Badu', 30])
print(person.items())   # dict_items([('first_name', 'Shivraj'), ('last_name', 'Badu'), ('age', 30)])

Adding and Updating Items

You can add new items or change the value of existing items using the assignment operator.

# Add a new item
person["city"] = "New York"

# Update an existing item
person["age"] = 31

print(person)

Conclusion

Dictionaries are a powerful and flexible data structure in Python. Their ability to store data in key-value pairs makes them ideal for a wide range of applications, from simple data storage to complex data mapping. If you need to store data that has a clear relationship between a key and a value, a dictionary is the perfect tool for the job.