Now that we’ve had a refresher on some of the built-in containers Python provides, let’s dive into the collections module.

The classes from the collections module are very similar to the built-in containers we’ve been already using, but they contain new methods and utilities. Each of these specialized containers focuses on a certain improvement to its built-in counterpart such as optimizing performance, better organization, fewer steps for performing tasks, and more!

In order to use classes from the collections module, we will first need to import the module into our code. This is different than the previous containers we’ve seen because they were built-in and did not require an import.

Here are some of the various ways importing will look like:

# To import a single class or multiple classes
from collections import name_of_class, name_of_another_class

# To import all classes in the collections module
from collections import *

# Another way to import all classes in a module
import collections

For a more specific example, here is what importing the OrderedDict (one of the specialized containers) would look like. We will dive deeper into the details of this particular container later on in this lesson but for now just observe the syntax:

from collections import OrderedDict

orders = OrderedDict({'order_4829': {'type': 't-shirt', 'size': 'large', 'price': 9.99},
          'order_6184': {'type': 'pants', 'size': 'medium', 'price': 14.99},
          'order_2905': {'type': 'shoes', 'size': 12, 'price': 22.50}})

orders.move_to_end('order_4829')
orders.popitem()

You might have noticed that this is a similar example to the dictionary review in the last exercise, but there are some new methods that provide even more functionality to the traditional dictionary.

Here is a list of all of the advanced containers we will be looking at in this lesson:

Advanced Containers

• deque
• namedtuple
• Counter
• defaultdict
• OrderedDict
• ChainMap

Container Wrappers

• UserDict
• UserList
• UserString