The Quick Python Book, Fourth Edition

7 Dictionaries

This chapter covers

• Defining a dictionary
• Using dictionary operations
• Determining what can be used as a key
• Creating sparse matrices
• Using dictionaries as caches
• Trusting the efficiency of dictionaries

This chapter discusses dictionaries, Python’s name for associative arrays or maps, which it implements by using hash tables. Dictionaries are amazingly useful, even in simple programs.

Because dictionaries are less familiar to many programmers than other basic data structures such as lists and strings, some of the examples illustrating dictionary use are slightly more complex than the corresponding examples for other built-in data structures. It may be necessary to read parts of chapter 8 to fully understand some of the examples ...