Creating and accessing dictionaries

The CUSIP number is a nine-digit alphanumeric number used to identify most securities owned by American and Canadian companies. Let's suppose that in your work at a FinTech startup, you are tasked with writing reports for clients. Your internal reports use CUSIP numbers, but your clients need to see stock symbols. Create a mapping of CUSIP numbers to stock symbols that makes it easy to do lookups. A dictionary is an ideal data structure for this kind of mapping as it lets you do fast lookups based on a key-value (the CUSIP number in this case).