11th lesson of Python Learning-basic data type (DICT)

• Dictionary

A dictionary consists of a key-value pair, consisting of a key (name) and a value that differs from the list and tuple is that the element inside is a key (name), So when you want to print the dictionary, print the dictionary variable plus [Key] Can

The dictionary comes with a function:

Function	Function
Clear ()	Delete all elements in a dictionary
Copy ()	Returns a copy of the dictionary (shallow copy)
Get (Key)	The key to the dictionary dict, returns the value it corresponds to, and returns the value of default if the key does not exist in the dictionary
Items ()	Returns a list that contains a tuple (key, value) in the dictionary
VALUES ()	Returns a list that contains all the values in the dictionary
Key ()	Returns a list containing the keys in the dictionary
Len (self)	Returns the number of keys in Dict
Pop (key)	Similar to method get (), if the key key exists in the dictionary, delete and return Dict[key], if the key key does not exist and the value of default is not given, the Keyerror exception is thrown
Del ()	Del dictionary variable. [Element key to delete]

Note : Parameters:

K: Key to search for

D: Default is NULL, returns the default value if the key does not exist

The function operates as follows:

#!/usr/bin/env python#-*-coding:utf-8-*-dict={"Zou": 2,"Lu"75A"Chen": 6}a=dict.copy ()Print(a)#print out {' Chen ': 6, ' Lu ': 5, ' Zou ': 2}b=["Bob","John"]Print(Dict.fromkeys (b,8))#Print new Dictionary {' Bob ': 8, ' John ': 8}Print(Dict.get ("Zou"))#Printing 2Print(Dict.items ())#Print [(' Chen ', 6), (' Lu ', 5), (' Zou ', 2)]Print(Dict.keys ())#print [' Chen ', ' Lu ', ' Zou ']Print(Dict.values ())#Print [6, 5, 2]Print(Dict.pop ("Lu"))Print(dict)#Print {' Chen ': 6, ' Zou ': 2} Delete {"Lu": 5}Print(Len (dict))#print back the number of keys in Dictdict.clear ()Print(dict)#Print {} Empty dictionary

Common actions : index new Delete key, value, key value pair loop length

# !/usr/bin/env python # -*-coding:utf-8-*-dict={"Zou": 2,"lu": 5,"  Chen": 6}print(dict["lu"])        # print "Lu" key 5

For loop

#!/usr/bin/env python#-*-coding:utf-8-*-dict={"Zou": 2,"Lu"75A"Chen": 6} forBinchdict:Print(b)#Print all the keys of Dict Chen Lu Zou#because the dictionary is unordered, the key order of the printed dictionary is different from the original dictionary forCinchdict:Print(Dict[c])#Print out 6 5 2

(items: Get keys and values) combined for loop

#!/usr/bin/env python#-*-coding:utf-8-*-dict={"Zou": 2,"Lu"75A"Chen": 6} forKvinchDict.items ():#because the items () get the keys and values, so in the loop to customize two variables representing the key and the value    Print(k)Print(v)#Print Chen 6 lu 5 Zou 2 loop out the dictionary keys and Values

Verify that the keys and values are in the dictionary:

#!/usr/bin/env python#-*-coding:utf-8-*-dict={"Zou": 2,"Lu"75A"Chen": 6}a="Zou" inchDict.keys ()Print(a) b=2inchdict.values ()Print(b)

Update (self, e=none)

(Append update) to append updated variables

#!/usr/bin/env python#-*-coding:utf-8-*-dict={"Zou": 2,"Lu"75A"Chen": 6}b={"Bob": 1,"John": 4,"Lin": 3}dict.update (b)Print(dict)#Print {' Lu ': 5, ' Zou ': 2, ' Chen ': 6, ' Bob ': 1, ' John ': 4, ' Lin ': 3}

Delete the elements in the dictionary

format:del dictionary variable. [Element key to delete]

 #  !/usr/bin/env python  #  -*-coding:utf-8-*- b={"  bob   ": 1,  " john   ": 4,"  lin   ": 3}   del  b[ john   "  " print   (b)  #   print {' Bob ': 1, ' Lin ': 3} Delete "John" key  

Some common methods:

__contains__ (...)

D.__contains__ (k)-True if D has a key k, else False

if the dictionary D contains the key K, then returns True, otherwise false

Similar functions:

Has_key (...)

D.has_key (k)->true if D has a key K, else false# returns True if dictionary D has key K, otherwise False

Items (...)

D.items ()->list of D ' s (key, value) pairs, as 2-tuples

#返回包含D的键值对的列表list, the element in list is a tuple with 2 data

Iteritems (...)

D.iteritems ()->an iterator over the (key, value) items of d# return an iterator object, each element is a key value pair (key, value)

Iterkeys (...)

D.iterkeys () A iterator over the keys of d# returns an iterative object with each element being a key to dictionary D

Itervalues (...)

D.itervalues-A iterator over the values of d# returns an iterative object with each element being a value of dictionary D

Functions of the Dictionary

Index

Increase

Delete

For loop

Length

Item

Key

Value

Determine if an element exists

Update

11th lesson of Python Learning-basic data type (DICT)