Understanding Python Dictionaries

How does Python handle dictionaries and how can we update and retrieve values from them? Python dictionaries are mutable, unordered collections that store key-value pairs. This data structure allows for efficient lookups, insertion, and deletion of elements. We can update a dictionary by adding, modifying, or removing key-value pairs. To update a dictionary, we can use the `update` method or simply assign a new value to a key. To retrieve a value from a dictionary, we can use the `get` method or directly access the value using the key.

When working with dictionaries in Python, it is important to understand how to update and retrieve values efficiently. Let's take a look at an example using Python dictionaries:

Example:

Suppose we have the following dictionary:

my_dict = dict(bananas=1.59, fries=2.39, burger=3.50, sandwich=2.99)

We can update this dictionary by adding new key-value pairs using the `update` method:

my_dict.update(dict(soda=1.49, burger=3.69))

This code segment adds two new key-value pairs to the dictionary: soda=1.49 and burger=3.69. If a key already exists in the dictionary, its value will be updated to the new value.

To retrieve a value from the dictionary, we can use the `get` method:

burger_price = my_dict.get('burger', 0)

The `get` method returns the value associated with the specified key. If the key is not found in the dictionary, it returns the default value provided as the second argument (in this case, 0).

Finally, we can print the value of the 'burger' key:

print(burger_price)

When we run this code segment, the output will be 3.69. This is because the `update` method updated the value for the key 'burger' to 3.69 in the dictionary. When we used the `get` method to retrieve the value for the 'burger' key, it returned 3.69.

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