python declare dictionary

(dict2,10) print (DICT4) #字典 (Dictionary) get () function returns the value of the specified key if the value does not return a default value in the dictionary. dict5={' name ': ' Gyh ', ' Age ':25}print (dict5.get (' name ', ' haha ')) print (Dict5.get (' name ', ' haha ')) #字典 ( Dictionary) update () function updates the

Common definition methods for Python dictionaries Define a dictionary directlyDict1 = {' x ': 1, ' Y ': 2, ' Z ': 3} Define a dictionary using the Dict methodDict2 = Dict (X=1, y=2, z=3) Define a dictionary using the Dict methodDict3 = Dict ((' x ', 1), (' Y ', 2), (' Z ', 3))) Dict built-in method

The code is as follows Copy Code #!/usr/bin/env python#-*-Encoding:utf-8-*-Dict2 = {}A = ' a 'Dict2.setdefault (a,1) #加入一个键和值 a,1A = ' B 'Dict2.setdefault (a,1) #加入一个键和值 b,1A = ' a 'Dict2.setdefault (a,2) #加入一个键和值 a,1, the resulting duplicate key cannot be repeated by adding {' A ': 1, ' B ': 1}Print Dict2#遍历key和valueFor key in Dict2.keys ():print ' key ', key, ' value ', Dict2[key]Print Dict2.has_key (' name ') #判断是否含有一个key

= {' name ': ' Tom ', ' Age ': '}dict1.pop ' print dict1 run result: {' name ': ' Tom '} 　　12,popitem randomly Delete Keydict1 = {' name ': ' Tom ', ' Age ': '}dict1.popitem ' () print Dict1 run result: {' name ': ' Tom '} 　　13,setdefault if the key is not in the dictionary, set the key and value, and if so, use the default and return the corresponding values. Dict1 = {' name ': ' Tom ', ' Age ': '}dict1.setdefault

This article mainly introduces the usage of the Dictionary (Dictionary) in python and provides detailed analysis of common operations such as creating, adding, and deleting a Python Dictionary in the form of an instance, for more information about the

First, what is a dictionaryA dictionary is the only type of mapping in the Python language.A hash value (key, key) and a pointer to an object (values, value) are a one-to-many relationship that is often considered a mutable hash table in the mapping type object.The Dictionary object is mutable, which is a container type that can store any number of

Python converts string and dictionary types. This document describes how to convert string and dictionary types in Python by using examples. The specific method is as follows: 1. convert a dictionary (dict) to a string (string) We can easily convert the

The dictionary in Python belongs to an advanced data structure, which is based on the hash table, and the complexity of the hash table in finding an element is basically O (1), so it is a very useful data structure. The following is a brief introduction to the operation of some dictionaries of capitalCreate a dictionary, assign a value to a dictionarynamerank={}n

Basic python tutorials-A Dictionary of notes Create dictionary A dictionary consists of multiple key-value pairs. Each key and corresponding value are separated by a colon, and items are separated by a comma. The entire dictionary is enclosed by a pair of braces, as shown

DictionarydictionaryPython uses {} or dict() creates an empty dictionary:{} dict()Type(a DictAfter you have dict, you can add elements to them by using the index key values, or you can view the values of the elements by index:Insert key value:a["one"] = "This is number 1" a["both"] = "This was number 2" a{' one ': ' This is number 1 ', ' both ': ' This is number 2 '}　　Dictionaries have no orderWhen we have print a

Python has three built-in data structures: list, ancestor, and Dictionary. This article introduces these three data structures and provides examples, let's take a closer look at the differences between the three. 1. list) List is the data structure that processes a group of ordered projects. you can store a series project in a list. The items in the list should be included in square brackets so that

Dictionary: an object associated with an array or a hash list that can be indexed by a keyword. Usage: defines an object that can contain multiple named fields, it can also be used as a container dictionary to quickly search for unordered data. it is the most comprehensive data type in python. it is most commonly used in programs to store and process data diction

Python first recognizes complex data types (list, dictionary, and tuple) and pythontuple In the previous article, we briefly understood the data types: number and string. In this article, we will introduce the heavyweight data types: list, dictionary, and metadata tuple. I. List: ① What is the list? For example, if I am a Tom, we can write me = 'Tom 'when definin

, the result of the output:Ainfo = {' ab ': ' liming ', ' ac ': ' Sex ': ' Man ', ' Age ': 20}>>> ainfo = {' ab ': ' liming ', ' AC ': 20}>>> ainfo[' sex ']= ' man '>>> ainfo[' age ']=20>>> Ainfo{' AC ': ' AB ': ' liming ', ' age ': ' + ' sex ': ' Man '}>>> ainfo.update ({' Sex ': ' Man ', ' Age ': 20})>>> Ainfo{' AC ': ' AB ': ' liming ', ' age ': ' + ' sex ': ' Man '}2 output result: [' ab ', ' AC ']>>> Ainfo.keys () [0:2][' AC ', ' AB ']3 output result: [' liming ', 20]4 returns the value of

,value)8, the update has 2 kinds of writing, such as the existence of key, update value, does not exist key to create a new key and set the valueDic.update ({' K1 ': ' 111111 ', ' K3 ': 123})Dic.update (k1=123,k3=345,k5= "ASDF")9. Returns the key value of the dictionaryDic.keys ()10. Returns the value of the dictionaryDic.values ()Description of the Dict dictionary1, with {} included, middle with, split, a pair of key values for middle use: Split2. Value in the

)False: Roman numerals, Chinese numeralsError:byte number (single byte)32, S.isnumeric (), BOOLWhether the string contains only numbersTrue:unicode numbers, full-width numerals (double-byte), Roman numerals, Chinese numeralsFalse: NoneError:byte number (single byte)33, S.isdigit (), BOOLWhether the string contains only numbersTrue:unicode number, byte digit (single byte), full-width digit (double byte), Roman numeralsFalse: Chinese numeralsError: None34, S.isspace (), BOOLWhether the string cont

. TuplesLists are similar to tuples, lists are mutable, tuples are immutable# # String Conversion Narimoto Group:str1 = ' ABCDEFGHIGKLMN 'Print (tuple (STR1))(' A ', ' B ', ' C ', ' d ', ' e ', ' f ', ' g ', ' h ', ' I ', ' g ', ' k ', ' l ', ' m ', ' n ')# # Tuple AA = (' A ', ' B ', ' C ', ' abc ', ' Hello ')When you have a single tuple, be careful to add commas :b = (' mn ',)Print (type (b))Otherwise, the Python parser is not recognized as a tuple

DictionaryDictionaries, as the name implies, are similar to those of the Xinhua dictionary in our Lives. So since it is also called a dictionary in Python, there must be some connection between the two. First of all, let's think about the way we use dictionaries in general. According to pinyin search, according to the radical search and so on ... So the question

3, Del d[' a '] #删除键值为 ' a ' element Traversing elements For K in D: print ' d[%s]= '% k,d[k] Or For k,v in D.items (): print ' d[%s]= '% k,v Or For k,v in D.iteritems (): print ' d[%s]= '% k,v Or For k,v in D.viewitems (): print ' d[%s]= '% k,v Items (), Iteritems () and viewitems () differences Python2.x's items () is a list that contains all the elements of dict, like the one above, but because of this too much memory, it was later added (note: The beginning of

The following small series will bring you a python dictionary (dict) key and value sorting. I think this is quite good. now I will share it with you and give you a reference. Let's take a look at the following small series to bring you a python dictionary (dict) key and value sorting. I think this is quite good. now I