Python Learning note 06-Dictionaries

Dictionary:

Unique mapping type in Pytho, unordered list (hash table)

Objects are mutable, but dictionary keys must use immutable objects, and different types of key values can be used in a dictionary

Definition method:-{} such as: Dic={name: ' Zzc ', Age:19,gender: ' Man '}

-Using the Factory Method Dict () column fdict=dice ([' X ', 1],[' Y ', 2])

-Built-in method: Fromkeys () The elements in the dictionary have the same value, default to None

Column: Ddict=[].fromkeys (' x ', ' Y '),-1)
Operation:

-Added: dic[' key ']= ' value '

-Modified: dic[' key ']= ' value '

-Delete a key and Value:del (dic[' key ') in the dictionary

-Delete and display the deleted value after deletion: dic.pop[' key '

-Delete all elements of the Dictionary: Dic.clear ()

-Delete entire dictionary: del dic

Method of the Dictionary:

+dic.clear: Delete all elements in the dictionary

+dic.fromkeys (Seq,val=none) creates and returns a dictionary with the elements in the SEQ, and Val is the default value set

+dic.get (Key,default=none): Returns the value of key if the key does not exist return Fefault specified

+dic.has_key (Key): Determine if there is a key in the dictionary, it is recommended to use in and not in instead of

+dic.keys () returns a list of keys in the dictionary

+dic.items () Returns a list of the corresponding tuples of the key value

+dic.iter* () Iteritems () Iterkeys () returns the iteration value instead of the list

+dic.setdefault (Key,default=none) with set, if key exists return its value, if key does not exist Dic[key]=default

+dic.update (DIC1) adds the key-value pairs in the Dic1 to the dictionary dic, and if duplicates overwrite, entries that do not exist in the original dictionary are added

+dic.valuse () Returns a list of all values in the dictionary

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Python Learning note 06-Dictionaries