12.2. Dictionary Operations

The del statement removes a key-value pair from a dictionary. For example, the following dictionary contains the names of various fruits and the number of each fruit in stock. If someone buys all of the pears, we can remove the entry from the dictionary.

Activity: CodeLens 12.2.1 (ch12_dict4)

Dictionaries are also mutable. As we’ve seen before with lists, this means that the dictionary can be modified by referencing an association on the left hand side of the assignment statement. In the previous example, instead of deleting the entry for pears, we could have set the inventory to 0.

Activity: CodeLens 12.2.2 (ch12_dict4a)

Similarily, a new shipment of 200 bananas arriving could be handled like this.

Activity: CodeLens 12.2.3 (ch12_dict5)

Notice that there are now 512 bananas—the dictionary has been modified. Note also that the len function also works on dictionaries. It returns the number of key-value pairs:

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