PART 1 Chapter V: Cognitive dictionary

Lecture 1: Cognitive dictionary

1. Dictionary: The purpose is to easily search for a specific word (key), to find its definition (value).

Dictionary surrounded by {}
Key dictionary is a - value (entry) of the composition (key - value ":" segmentation, key - the value of use, "" splitting)
The dictionary is the only key, value may not be unique
Dictionary view the values of a key, the key is to go by the name of view, is through an index list

= {PhoneBook " Ann " : " 15,012,345,678 " , " Alice " : " 15,112,345,678 " }
 Print (PhoneBook)
 Print (PhoneBook [ " Alice " ])
 Print ( " ====== ==== view the elements in the list === " ) 
names = [ " Ann " , " Bob " ]
 Print (names)
 Print (names [0]) 


results: 

{ 'Ann': ' 15,012,345,678 ' , ' Alice ' : ' 15,112,345,678 ' }
 15,112,345,678 
====== view a list of elements ======= 
[ ' Ann ' , ' Bob ' ] 
Ann

Under the following circumstances, the dictionary is more practical than the list:

Represents a forward state of the game, each key is composed by the coordinate values of tuples;

Storage file modification time, with the file name as the key;

Digital phone / address book

2. dict function: it can be converted to a list or dictionary Ganso

phonebook = [("Alice","1234"),("Bob","2345")]
d = dict(phonebook)
print(d)
d["Ann"] = "3456"
print(d)
d["Alice"] = "1111"
print(d)


结果：

{'Alice': '1234', 'Bob' : ' 2345 ' } 
{ ' Alice ' : ' 1234 ' , ' Bob ' : ' 2345 ' , ' Ann ' : ' 3456 ' } 
{ ' Alice ' : ' 1111 ' , ' Bob ' : ' 2345 ' , ' Ann ' : ' 3456 '}

phonebook = (["Alice","1234"],["Bob","2345"])
d = dict(phonebook)
print(d)
d["Ann"] = "3456"
print(d)
d["Alice"] = "1111"
print(d)

结果：

{'Alice': '1234', 'Bob' : ' 2345 ' } 
{ ' Alice ' : ' 1234 ' , ' Bob ' : ' 2345 ' , ' Ann ' : ' 3456 ' } 
{ ' Alice ' : ' 1111 ' , ' Bob ' : ' 2345 ' , ' Ann ' : ' 3456 '}

3. The basic dictionary operations

len (d) d is returned item (key - value pairs) Number
D [k] to return to the associated value of k
d [k] = v v to the value associated with the key k
del d [k] is k delete key entry
in d d k check whether the entry contains k

= {PhoneBook " Ann " : " 15,012,345,678 " , " Alice " : " 15,112,345,678 " }
 Print (len (PhoneBook)) # Number of key-value pairs in the output dictionary 
Print (PhoneBook [ " Alice " ]) 
PhoneBook [ " Ann " ] = " 010-12345678 "  # change the key value 
Print (PhoneBook [ " Ann " ])
 del PhoneBook [ " Alice "] #Delete the corresponding key on the 
Print (PhoneBook) 

IF  " Ann "  in PhoneBook:
     Print (True)
 the else :
     Print (False) 

IF  " Alice "  in PhoneBook:
     Print (True)
 the else :
     Print (False) 


result:

 2 
15,112,345,678 
010 12345678 
{ ' Ann ' : ' 010-12345678 ' } 
True 
False

PART 1 Chapter V: Cognitive dictionary

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