Key Concepts

Review core concepts you need to learn to master this subject

Python dictionaries

Syntax of the Python dictionary

Dictionary value types

Accessing and writing data in a Python dictionary

Merging dictionaries with the .update() method in Python

get() Method for Dictionary

The .pop() Method for Dictionaries in Python

Dictionary Key-Value Methods

Python dictionaries

my_dictionary = {1: "L.A. Lakers", 2: "Houston Rockets"}

A python dictionary is an unordered collection of items. It contains data as a set of key: value pairs.

Creating Dictionaries
Lesson 1 of 2
  1. 1
    Introduction to Dictionary
    A dictionary is an unordered set of key: value pairs. It provides us with a way to map pieces of data to each other so that we can quickly find values that are associated with one another. Sup…
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  2. 2
    Make a Dictionary
    In the previous exercise, we saw a dictionary that maps strings to numbers (i.e., “avocado toast”: 6). However, the keys can be numbers as well. For example, if we were mapping restaurant bill su…
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  3. 3
    Invalid Keys
    We can have a list or a dictionary as a value of an item in a dictionary, but we cannot use these data types as keys of the dictionary. If we try to, we will get a TypeError. For example: powe…
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  4. 4
    Empty Dictionary
    A dictionary doesn’t have to contain anything. Sometimes we need to create an empty dictionary when we plan to fill it later based on some other input. We can create an empty dictionary like this:…
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  5. 5
    Add A Key
    To add a single key: value pair to a dictionary, we can use the syntax: dictionary[key] = value For example, if we had our menu dictionary from the first exercise: menu = {“oatmeal”: 3, “avocad…
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  6. 6
    Add Multiple Keys
    If we wanted to add multiple key : value pairs to a dictionary at once, we can use the .update() method. Looking at our sensors object from a previous exercise: sensors = {“living room”: 21, “kit…
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  7. 7
    Overwrite Values
    We know that we can add a key by using syntax like: menu[“avocado toast”] = 7 This will create a key “avocado toast” and set the value to 7. But what if we already have an ‘avocado toast’ entry …
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  8. 8
    Dict Comprehensions
    Let’s say we have two lists that we want to combine into a dictionary, like a list of students and a list of their heights, in inches: names = [‘Jenny’, ‘Alexus’, ‘Sam’, ‘Grace’] heights = [61, 70…
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  9. 9
    Review
    So far we have learned: - How to create a dictionary - How to add elements to a dictionary - How to update elements in a dictionary - How to use a list comprehension to create a dictionary from two…
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