python data structures tutorial

made up of several comma-separated values, and the tuple is immutable.CollectionA collection is a set of unordered, non-repeating elements. Basic features include relationship testing and elimination of duplicate elements .>>> x = set()>>> xset()>>> x.add(123)>>> x{123}>>> x.add(123)>>> x{123}>>> x.add(1)>>> x{1, 123}>>> a = set(‘abracadabra‘)>>> b = set(‘alacazam‘)>>> a-b #求差，即在a中不在b中{‘r‘, ‘d‘, ‘b‘}>>> a | b # 在a中出现 或者在b中出现{‘r‘, ‘z‘, ‘l‘, ‘m‘, ‘d‘, ‘b‘, ‘a‘, ‘c‘}>>> a ^ b # 只在a 中出现 或只在b中出现{‘r‘

Data structures for Redis: Redis is a data structure for key-value, and each data is a key-value pair The type of the key is a string Note: Keys cannot be duplicated The value of Redis is divided into five types: Strings string Hashed Hash Lists List Set Set Ordered set Zs

equivalent to the first step of the tapply () function, and omits subsequent application function operations. Basic invocation form: Split (x, F), where x can be a vector or a data frame (the tapply () function cannot be a data frame), and F is a list of factors or factors. The return value is a list.By () function: In a way similar to the tapply () function, they are grouped first, and then the function i

Course IntroductionIn the field of mathematics science, Python is already the mainstream programming language, this course is based on the Python language to explain the data analysis, machine learning, common analysis tools, data visualization and text processing technology.Directory00. Pre-Class preview (

transforms the data iteratively, saving memory#determine if any. py files exist in a directoryImportOsfiles= Os.listdir ('dirname')ifAny (Name.endswith ('. PY') forNameinchfiles):Print('there be python!')Else: Print('Sorry, no python.')#Output a tuple as CSVs = ('ACME', 50, 123.45)Print(','. Join (STR (x) forXinchs)) #join the object being processed is a stri

Set (set) is a very useful data structure. It behaves like a list, except that a set cannot contain duplicate values.This is useful in many cases. For example, you might want to check if the list contains duplicate elements, you have two choices, and the first one needs to use a For loop, like this:#use a For loop to check for duplicate elementsSome_list = ['a','b','C','b','D','m','N','N','b']dup= [] forValueinchsome_list:ifSome_list.count (value) >2:

SSDBA high-performance NoSQL database that supports rich data structures to replace Redis.Characteristics 100 times times the capacity of Redis instead of Redis database LevelDB network support, using C + + development Redis API compatible, support for Redis clients Suitable for storing collection data, such as list, hash, zset ... The la

(vector, dimensions, dimnames), where the vector contains the elements in an array, dimensions is a vector that specifies the size of each dimension of the array, and Dimnames is a list that specifies the names of each dimension.Data frame:Data frame is our common data storage method for data analysis, and each row of the database corresponds to a record, each column corresponds to a field,

This article mainly introduces the basic data types and variable declaration in the basic python tutorial. it first introduces some knowledge about variable declaration and then lists the most common basic data types, for more information, see Variable does not need to be declared

;deff (x, y): -...return10*x+y + ... ->>> B = Np.fromfunction (f, (5,4), dtype=int) +>>>b AArray ([[[0, 1, 2, 3], at[10, 11, 12, 13], -[20, 21, 22, 23], -[30, 31, 32, 33], -[40, 41, 42, 43]]) ->>> b[2,3] -23 in>>> B[0:5, 1]#second column -Array ([1, 11, 21, 31, 41]) to>>> b[:, 1]#second column +Array ([1, 11, 21, 31, 41]) ->>> B[1:3,:]#second row, third row theArray ([[[10, 11, 12, 13], *[20, 21, 22, 23]]) $GT;GT;B[-1]#equivalent to B[-1,:], last linePanax NotoginsengArray ([40, 41, 42, 43])

we encapsulated, and then left the interface for external useAbstract data types have a bit of an object-oriented sense, the same data type, such as stack, we can write in Python, we can write in C (the object of C is not so strong), but we call the pop function, the return is the stack on the top element, And ElementType just tell us this stack can be installed

the first chapter: Data structure and algorithmIntroduction: This book is advanced usage, not small white use bookPurpose: The purpose of writing is to record the process of learning the book and the Harvest1.1 The decompression sequence is assigned to multiple variables:problem : There is now one containing n elements of a tuple or a sequence, how to extract the value inside it and assign a value to n variables?Solution: extract and assign values to

A. TableThe table is the only data structure for LUA. The table is the most important data type in Lua. The table is similar to a dictionary in Python. A table can only be created by a stereotype. Other data structures provided in other languages, such as array, list, and so

filtering is the Bloom filter (Bron filter). The Bron filter principle is simply: Create a large bit array, then hash the same URL with multiple hash functions to get multiple numbers, and then position the digits in the bit array at 1. Next time a URL, the same is used to hash the hash function, to get multiple numbers, we only need to determine the bit array of these numbers corresponding to is all 1, if all is 1, then the URL has appeared. This completes the URL-heavy issue. Of course, this

Advantages and disadvantages of the 1.XML and JSON two data structures1> XMLAdvantages:? uniform format , standards-compliant? Easy to interact with other systems remotely , data sharing is more convenient ? Disadvantages: XML file format file is large , complex format , transmission consumption bandwidth ? Both the server side and the client need to spend a lot of code parsin

issue. It is great article to use relational databases to access or to use NoSQL, or to design specific file formats for storage.6) Inter-process communicationDistributed crawler, it is necessary to rely on inter-process communication. We can interact with data in the specified data format to complete interprocess communication.7) ...Nonsense said so much, the real problem comes, the problem is not to lear

intentionally so designed, is for example to avoid the program relies on some kind of hash implementation, the purpose is for the program's robustness. If you do not want to traverse sequentially, you must display the sort key, and you can use the string function in the sort package. The code below is generally best not to use this way.Import "Sort"var names []stringFor, Name: = Range Ages {names = append (names, name)}Sort. Strings (names)for, Name: = range Names {Fmt. Printf ("%s\t%d\n", Name

Python crawler tutorial -24-Data Extraction-BEAUTIFULSOUP4 (ii)This article describes how BS traverses a Document objectTraversing Document objects Contents:tag child nodes are exported as a list Children: Child nodes are returned as iterators Descendants: All descendant nodes String: Prints the specific contents of the label with a string wi

", "Key": "V1001_today_music" } , "2": { "t Ype ":" click "," Name ":" Singer Profile "," Key ":" V1001_today_singer "} ," 3 ": { "name": "Menu", "Sub_button": [{ "type": "Vie W "," Name ":" Search "," url ":" http://www.soso.com/"} , { "type": "View", "Name": "Video", "url": "HT tp://v.qq.com/"} , {" type ":" Click ", "Name": "Like Us", "Key": "V1001_good" }]}}} It is inconsistent to see the form.Just look at the structure of the JSON.JSON has two kinds

iteration, put the corresponding content in the iterable into the Iter_var, and then apply the content of the Iter_var in the expression, Finally, a list is generated with the calculated value of the expression. than we're going to generate a list containing 1 to 10 >>> [x for x in range (1,11)] [1, 2, 3, 4, 5, 6, 7, 8, 9, ten] >> 2. Added the judgment statement, only satisfies the condition content to put in the iterable the corresponding content in the Iter_var, then applies the conten