Nested Dictionaries

Section 10.2 Nested Dictionaries

Just as lists can contain items of any type, the value associated with a key in a dictionary can also be an object of any type. In particular, it is often useful to have a list or a dictionary as a value in a dictionary. And of course, those lists or dictionaries can also contain lists and dictionaries. There can be many layers of nesting.

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Only the values in dictionaries can be objects of arbitrary type. The keys in dictionaries must be one of the immutable data types (numbers, strings, tuples).

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Check Your Understanding

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Checkpoint 10.2.1.

Which of the following is a legal assignment statement, after the following code executes?

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d = {'key1': {'a': 5, 'c': 90, 5: 50}, 'key2':{'b': 3, 'c': "yes"}}

d[5] = {1: 2, 3: 4}
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5 is a valid key; {1:2, 3:4} is a dictionary with two keys, and is a valid value to associate with key 5.
d[{1:2, 3:4}] = 5
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Dictionary keys must be of immutable types. A dictionary can’t be used as a key in a dictionary.
d[’key1’][’d’] = d[’key2’]
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d[’key2’] is {’b’: 3, ’c’: "yes"}, a python object. It can be bound to the key ’d’ in a dictionary {’a’: 5, ’c’: 90, 5: 50}
d[key2] = 3
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key2 is an unbound variable here. d[’key2’] would be OK.

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Checkpoint 10.2.2.

1. Extract the value associated with the key color and assign it to the variable color. Do not hard code this.

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