and care about compatibility (or suspect that you might someday)here are some pointers of the changes we've met in this sectionthe first (dictionary comprehensionscan be coded only in and the second (dictionary viewscan be coded only in xand with special method names in howeverthe last three techniques--sortedmanual comparisonsand in--can be coded in today to ease migration in the future why you will caredictionary interfaces dictionaries aren' just convenient way to store information by key in your programs --some python extensions also present interfaces that look like and work the same as dictionaries for instancepython' interface to dbm access-by-key files looks much like dictionary that must be opened you store and fetch strings using key indexesimport dbm file dbm open("filename"file['key''datadata file['key'named anydbm in python link to file store data by key fetch data by key in you'll see that you can store entire python objects this waytooif you replace dbm in the preceding code with shelve (shelves are access-by-key databases that store persistent python objectsnot just stringsfor internet workpython' cgi script support also presents dictionary-like interface call to cgi fieldstorage yields dictionary-like object with one entry per input field on the client' web pageimport cgi form cgi fieldstorage(parse form data if 'namein formshowreply('helloform['name'valuethough dictionaries are the only core mapping typeall of these others are instances of mappingsand support most of the same operations once you learn dictionary interfacesyou'll find that they apply to variety of built-in tools in python for another dictionary use casesee also ' upcoming overview of json-- language-neutral data format used for databases and data transfer python dictionarieslistsand nested combinations of them can almost pass for records in this format as isand may be easily translated to and from formal json text strings with python' json standard library module summary in this we explored the list and dictionary types--probably the two most commonflexibleand powerful collection types you will see and use in python code we learned that the list type supports positionally ordered collections of arbitrary obsummary