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Python’s Four Main Containers

Python has four built-in classes that are used to create objects that store other objects.

They are: tuple, list, set and dictionary.

We’ll cover them all in detail in the following pages, but here’s a brief summary of what they’re used for and some example code.

# Tuple
c1 = (2, 6, 9)

# List
c2 = ["One", "Two", "Three"]

# Set
c3 = {"dog", "cat", "horse"}

# Dictionary
c4 = {"Mon": "Monday", "Tue": "Tuesday", "Wed": "Wednesday"}
(2, 6, 9)
['One', 'Two', 'Three']
{'horse', 'dog', 'cat'}
{'Mon': 'Monday', 'Tue': 'Tuesday', 'Wed': 'Wednesday'}
  • tuple allows you to create a list of objects of any types. They remain in the order you put them. Once you’ve created a tuple, you can’t change it: it’s immutable.
  • list is similar to tuple except you can modify it, adding or removing items: it’s mutable.
  • set stores unique objects: you can’t have the same object twice in a set. It does not maintain any particular order.
  • dict (dictionary) lets you store key-value pairs, so it’s essentially a lookup table. In older versions of Python dict was not ordered, but in more recent versions of Python, dict will keep objects in the order you specified.

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