Python Dictionary Type Usage example

dictionary ispythonThe unique mapping type in the language, with curly braces{}indicates that a dictionary entry is a key-value pair, and the methodkeys ()returns the list of keys for the dictionary,values ()returns a list of values for the dictionary,items ()returns a list of key-value pairs for the dictionary. There are no restrictions on the values in the dictionary, they can be anypythonobject, but the keys in the dictionary are type-restricted, each key can only correspond to one value, and the key must be a hardy, and all immutable types can be hashed. Immutable CollectionsFrozensetcan be used as a dictionary key, but a mutable collectionSetwill not.

The following are common methods for dictionary types.

Clear () : Deletes all the elements in the dictionary.

copy () : Return Returns a copy of the dictionary (shallow copy).

Fromkeys (seq,val=none) : Create and return a new dictionary to seq val Span style= "Font-family:wenquanyi Micro Hei" > do the initial value corresponding to all the keys in the dictionary.

get (key,default=none) : Returns the keys in the dictionary key value default

Has_key (Key): If the keyKeyexists in the dictionary, returnsTrue, or returnFalse. python2.2after this method is almost obsolete, it is usually usedinchto replace.

items () : Returns a list that contains the tuple of key values in the dictionary.

keys () : Return Returns a list containing the keys in the dictionary.

ITER () : Party Method iteritems () , iterkeys () , itervalues () Same as the non-iterative methods they correspond to, The difference is that they return an iteration instead of a list.

pop (Key[,default]): and Methodsget ()Similarly, if the dictionaryKeykey exists, deleted and returnedDict[key], ifKeykey does not exist, and does not givedefaultthe value that is thrownKeyerrorexception.

Setdefaul T (key,default=none) : And method get () similar if is not present in the dictionary key key, by dict[key]=default

Update (DICT2) : the dictionary Dict2 The key value pair is added to the current dictionary.

values () : Returns a list that contains all the values in the dictionary.

The following is an example of the use of a dictionary using a data system that emulates user logins .

#!/usr/bin/env python db = {} def newuser (): prompt = ' register: ' While true:name = Raw_input (Prompt) if Db.has_key (name  ): prompt = ' name taken, try another: ' Continue else:break pwd = Raw_input (' passwd: ') db[name] = pwd  def olduser (): Name = Raw_input (' login: ') pwd = Raw_input (' passwd: ') passwd = db.get (name) if passwd = = Pwd:print ' login success: ', n  Ame else:print ' login failure ' def showmenu (): prompt = "" "(R) Eister (L) ogin (Q) uit Enter choice:" "" Done = False while Not Done:chosen = False and not chosen:try:choice = Raw_input (Prompt). Strip () [0].lower () except (Eoferror, Keyboardi Nterrupt): choice = ' q ' print ' \nyour choice: [%s] '%choice if choice not in ' RLQ ': print ' invalid option, try again ' else : chosen = true if choice = = ' R ': NewUser () elif choice = = ' L ': olduser () Else:done = true if __name__ = = ' __main__ ': Sho Wmenu ()

the third line of the script initializes an emptyDBDictionary, section9Line throughHas_key ()determine the newly registered user name (the dictionary'sKey) is present, section theline through square brackets[]add a password to a user name (that is, add a value to a key), -Line throughget ()gets the password for the user name (that is, the dictionary'sKeycorresponding to thevalue). Section -Line ofstrip ()is a string-handling function that is used to remove whitespace from the end of a string.

Python Dictionary Type Usage example