Python cookbook (data structure and algorithm) is used to filter and extract elements in a sequence.
This article describes how to filter and extract elements in a sequence using Python. We will share this with you for your reference. The details are as follows:
Problem:Extracts values from a sequence or deletes the sequence according to certain criteria.
Solution:List derivation, generator expression, use
Python cookbook (data structure and algorithm) is used to break down elements from any length of iteratable objects.
This example describes how to use python to break down elements from iteratable objects of any length. We will share this with you for your reference. The details are as follows:
N elements are extracted from an Iterated object, but the length of the iterated object may exceed N, resulting in
1 What is data mining?
The most commonly accepted definition of "Data Mining" is the discovery"Models" for Data.
1.1 statistical modeling
Statisticians were the first to use the term "data min
Spatial Data
Multimedia Data
For example, image data
Description-based retrieval system: keywords, titles, dimensions, etc.
Content-based retrieval system: color composition, texture, shape, object and wavelet transformation.
Time series data and sequence data
Trend Analysis
First contact data mining related knowledge, worship Daniel's article, hope to be able to add their own understanding
What is clustering, classification, regression.
Article 1: Data mining commonly used methods (classification, regression, clustering, association rules, etc.), slightly to the conceptual interpretatio
If the object is an iterative (any sequence), it can be decomposed, including tuples, lists, strings, files, iterators, and generators, which can be decomposed into separate variables by a simple assignment operation.The only requirement: The total number of variables matches the sequence, otherwise an error will occur;Python 2.7.11 (v2.7.11:6d1b6a68f775, Dec 5, 20:32:19) [MSC v.1500 32bit (Intel)] on Win32type"Copyright","credits" or "license ()" forMore information.>>> p=[4,5]>>>p[4, 5]>>> x,
Purpose of collecting web logsWeb log mining refers to the use of data mining technology, the site user access to the Web server process generated by the log data analysis and processing, so as to discover the Web users access patterns and interests, such information on the site construction potentially useful and unde
errorTraceback (most recent): File"", Line 1,inchIndexerror:index out of range>>> Heappush (a,3)>>>a[3]>>> Heapreplace (a,2)#Delete (Heappop (a)->3) first, then join (Heappush (a,2))3>>>a[2]>>> Heappush (a,5) >>> Heappush (a,9)>>> Heappush (a,4)>>>a[2, 4, 9, 5]>>> Heapreplace (a,6)#first find the minimum value from heap A and return, then add 62>>>a[4, 5, 9, 6]>>> Heapreplace (a,1)#1 is added later, before 1, the minimum value in a is 4 .4>>>a[1, 5, 9, 6]>>> a=[2,4,6] >>> b=[1,3,5]>>>
=min (Zip (Prices.keys (), Prices.values ())) #zip () parameter is incorrect in order to get the wrong value>>>Min_price3 ('AAPL', 612.78)>>> Max_price3 =max (Zip (Prices.keys (), Prices.values ())) #zip () parameter is incorrect in order to get the wrong value >>>Max_price3 ('IBM', 205.55)>>>When doing these calculations, note that zip () creates an iterator whose contents can only be consumed once. For example:>>> pirces_and_names=Zip (prices.values (), Prices.keys ())>>> pirces_and_names mi
1 ImportCSV2 3filename ='Ch02-data.csv'4data = []5 6 Try:7with open (filename) as f://binding a data file to an object F with the WITH statement8Reader =Csv.reader (f)9Header = Next (reader)//python 3. X is for next ()Tendata = [row forRowinchReader] One exceptCSV. Error as E: A Print('Error reading CSV file at line%s:%s'%(reader.line_num,e)) -Sys.exit (-1) - the ifHeader: - Print(header) - Print("=======================") - forRowinchDa
the value of key is the set typec['a'].add (1) c['a'].add (2) c['a'].add (2) c['b'].add (4)Print('the value of key is a dictionary of the list type:', D)Print('the value of key is a dictionary of the set type:'C>>> ================================ RESTART ================================>>>the value of key is a dictionary of list type: Defaultdict (class 'List', {'b': [4],'a': [1, 2, 2]}) The value of key is a dictionary of the set type: Defaultdict (class 'Set', {'b': {4},'a': {1, 2}})>>>One t
Problem: You want to access the element by name to reduce the dependency on the location in the structureSolution: Use the named Tuple collections.namedtuple (). It is a factory method that returns a subclass of the standard tuple type in Python, gives it a type name and the corresponding field name , returns a class that can be instantiated, gives you a defined field name to pass in the value, and so on.The primary purpose of a named tuple is to decouple the code from the location of the elemen
Problem: Want to create a dictionary, which is itself a subset of another dictionarySolution: Use dictionary derivation (dictionary comprehension) to easily solve#example of extracting a subset from a dictionary fromPprintImportpprintprices= { 'ACME': 45.23, 'AAPL': 612.78, 'IBM': 205.55, 'HPQ': 37.20, 'FB': 10.75}#Make A dictionary of pricesP1 = {Key:value forKey, ValueinchPrices.items ()ifValue > 200 }Print("All prices") Pprint (p1)#Make A dictionary of tech stocksTech_names = {'AAPL
Python cookbook (data structure and algorithm) method for saving the last N elements, pythoncookbook
This example describes how to save the last N elements in Python. We will share this with you for your reference. The details are as follows:
Problem:We hope to make a limited history statistics for the last few records during iteration or other forms of processing.
Solution:Select collections. deque.
The fo
The n elements are decomposed from an iterative object, but the length of an iterative object may exceed N, and an exception of "too many decomposition values" appears.Use "* expression" to resolve the problem:Python 3.4.3 (v3.4.3:9b73f1c3e601, Feb, 22:43:06) [MSC v.1600 32bit (Intel)] on Win32type"Copyright","credits" or "license ()" forMore information.>>> *headdata,current=[10,3,2,6,8,5]#* Modified variables are located in the first position of the list, easy to separate head and tail>>>head
First, data mining
Data mining is an advanced process of using computer and information technology to obtain useful knowledge implied from a large and incomplete set of data. Web Data mining
In various data mining algorithms, association rule mining is an important one, especially influenced by basket analysis. association rules are applied to many real businesses, this article makes a small Summary of association rule mining. First, like clustering algorithms, association rule
I plan to organize the basic concepts and algorithms of data mining, including association rules Mining, classification, clustering of common algorithms, please look forward to. Today we are talking about the most basic knowledge of association rule mining.
Association rules minin
transaction by user shell+ip+ hostname according to different user's login (all three are the same user) Based on this, the basic principle of mining 2 algorithm for user input command sequence frequent pattern is realized.
The fp-growth algorithm mainly solves the collection of frequent items where the number of occurrences reaches a certain threshold in multiple sets. A FP tree is a compressed representation of input
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