Using Dictionaries
Get All Keys

Sometimes we want to operate on all of the keys in a dictionary. For example, if we have a dictionary of students in a math class and their grades:

test_scores = {"Grace":[80, 72, 90], "Jeffrey":[88, 68, 81], "Sylvia":[80, 82, 84], "Pedro":[98, 96, 95], "Martin":[78, 80, 78], "Dina":[64, 60, 75]}

We want to get a roster of the students in the class, without including their grades. We can do this with the built-in list() function:

>>> list(test_scores) ["Grace", "Jeffrey", "Sylvia", "Pedro", "Martin", "Dina"]

Dictionaries also have a .keys() method that returns a dict_keys object. A dict_keys object is a view object, which provides a look at the current state of the dicitonary, without the user being able to modify anything. The dict_keys object returned by .keys() is a set of the keys in the dictionary. You cannot add or remove elements from a dict_keys object, but it can be used in the place of a list for iteration:

for student in test_scores.keys(): print(student)

will yield:

"Grace" "Jeffrey" "Sylvia" "Pedro" "Martin" "Dina"



Create a variable called users and assign it to be a dict_keys object of all of the keys of the user_ids dictionary.


Create a variable called lessons and assign it to be a dict_keys object of all of the keys of the num_exercises dictionary.


Print users to the console.


Print lessons to the console.

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