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.
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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.
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Similarily, a new shipment of 200 bananas arriving could be handled like this.
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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:
Check your understanding
dict-2-1: What is printed by the following statements?
mydict = {"cat":12, "dog":6, "elephant":23}
mydict["mouse"] = mydict["cat"] + mydict["dog"]
print(mydict["mouse"])