When working with Python dictionaries, it is often necessary to extract specific values from within the dictionary. There are several methods to achieve this, each with its own advantages and disadvantages. In this article, we will explore three different approaches to get sub values from a Python dictionary.

Method 1: Using the get() method

The get() method is a built-in function in Python dictionaries that allows us to retrieve a value associated with a given key. It takes two arguments – the key we want to retrieve the value for, and an optional default value to return if the key is not found.

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
name = my_dict.get('name')
age = my_dict.get('age')
city = my_dict.get('city')

print(name)  # Output: John
print(age)   # Output: 25
print(city)  # Output: New York

This method is safe to use as it does not raise a KeyError if the key is not found in the dictionary. Instead, it returns None or the default value specified. However, it can be cumbersome to use if we need to extract multiple values from the dictionary.

Method 2: Using square brackets

In Python, we can access dictionary values directly using square brackets and the key name. This method is concise and straightforward.

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
name = my_dict['name']
age = my_dict['age']
city = my_dict['city']

print(name)  # Output: John
print(age)   # Output: 25
print(city)  # Output: New York

However, this method raises a KeyError if the key is not found in the dictionary. Therefore, it is important to ensure that the key exists before accessing it using this method.

Method 3: Using the items() method

The items() method returns a view object that contains key-value pairs of the dictionary. We can iterate over this view object to extract the desired values.

my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}
for key, value in my_dict.items():
    if key == 'name':
        name = value
    elif key == 'age':
        age = value
    elif key == 'city':
        city = value

print(name)  # Output: John
print(age)   # Output: 25
print(city)  # Output: New York

This method allows us to perform additional logic while extracting the values. However, it can be less efficient compared to the previous methods, especially when dealing with large dictionaries.

After considering these three methods, the best option depends on the specific requirements of your code. If you are certain that the key exists in the dictionary, using square brackets is the most concise and efficient method. However, if you need to handle cases where the key may not exist, the get() method provides a safe alternative. The items() method is useful when you need to perform additional logic while extracting the values.