python 2 7 book

Python BASICS (2) variables, process control, and python VariablesI. Variables Declare variables:Name = "Henry" # variable name: name, variable name value: "Henry" The role of a variable: nickname, which represents the content stored in an address in the memory. Variable definition rules: Variable names can only be any combination of letters, numbers, or unders

插入的Key的顺序返回[‘z‘‘y‘‘x‘]OrderedDictYou can implement a FIFO (first-in-one-out) dict, deleting the first added key when the capacity exceeds the limit:　　 fromCollectionsImportordereddictclasslastupdatedordereddict (ordereddict):def __init__(self, capacity): Super (Lastupdatedordereddict, self).__init__() self._capacity=capacitydef __setitem__(self, Key, value): ContainsKey= 1ifKeyinchSelfElse0ifLen (self)-ContainsKey >=Self._capacity:last= Self.popitem (last=False)Print 'Remove:', lastifContainsKey

Learn Python recently and summarize how to add a shell script to reach (object.) tab, press 2 to reduce the appearance of all methods.1, first in the directory:/usr/lib64/python2.7/site-packages below the creation of vim tab.py file.2. The following contents of the tab.py file:#!/usr/bin/pythonimport osimport readlineimport rlcompleterimport atexitimport os# tab

1. What if we want to restrict the properties of an instance? For example, only add and attributes to student instances are allowed name age .For the purpose of limiting, Python allows you to define a special variable when defining a class __slots__ to limit the attributes that the class instance can add:2, use __slots__ to note that the __slots__ defined properties only work for the current class instance,

Python game engine development (7): drawing vector Graphs Today, we will draw a vector image.Graphics class First, createGraphicsClass is used to create vector graphics: Class Graphics (DisplayObject): def _ init _ (self): super (Graphics, self ). _ init _ () # self. _ drawingList = [] # used to store the current graphic data self. _ currentGraphics = None Since our window interface is constantly being clea

‘:"Value1",‘Key2‘:{‘K1‘:‘V1‘,‘K2‘:[‘vv1 ", ' vv2 ' "}, "key3 ": 886, "key4": [ ' armin", Modifications to dictionaries and lists in nested:A_dict ={‘Key1‘:"Value1",‘Key2‘:{‘K1‘:‘V1‘,‘K2‘:[‘Vv1‘,‘Vv2‘]},‘Key3': 886,‘Key4‘:[‘Armin‘,‘Admin ", [1,2,3],{" k41 ": " v41 ' }]} A_dict[ "key4"][3][ ' n "]= "test" #向 Keys4 in the fourth element Add a key n value to test. a_dict[ "key4print (a_dict) Nested applications:A_dict =[ {"Name" :"Armin","Pwd" :"123"}, {"Name" :"Admin","Pwd" :"123

', Bdapi) -Response =Urllib.request.urlopen (Request) -Weatherinfo = Response.read (). Decode ('Utf-8') theJsondatas =json.loads (weatherinfo) - forKinchJsondatas.keys ():#there is actually only one key-value pair -Dictdatas =Jsondatas[k][0] - returnDictdatas + - + if __name__=='__main__': ADictdatas = Getcityweather ('Xian','xxxxxxxxxxxxxxxxxxxxxxxxxxx')#Replace city and Apikey at Print(dictdatas['Basic'][' City'])#Place Names - Print('Update Time:', dictdatas['Basic']['Updat

Python Web development framework-Django (2), python-django Next, I will introduce some practical skills and notes. The first time I used MarkDown for editing, I felt that the gap was too large and not so nice.GET/POST Data Interaction between the front and back ends. JQuery is used to implement get/post requests.GET Method 1: Use a regular expression to match ur

( ) This method returns a tuple of column names. Immediately after a query, it's the first member of each tuple in cursor.description. New in version 2.6. The following examples illustratein [+]: cx.row_factory = sqlite3. Rowin [+]: c = cx.cursor ()in [+]: C.execute (' select * from Catalog ')OUT[32]: In [all]: R = C.fetchone ()in [+]: type (R)OUT[34]: in [+]: ROUT[35]: In [approx]: print R(0, ten, U ' \u9c7c ', U ' Yu ')In [PNS]:

as a basis for dividing two classes. In combination with P/R analysis, the selection of threshold value can be more flexible and excellent.As you can see, if you choose a threshold that is too low, more test samples will be divided into 1 categories. Therefore, the recall rate can be improved, obviously the accuracy of the sacrifice of the corresponding accuracy rate.In this example, perhaps I would choose 0.42 as the dividing value-because the accuracy and recall rates are high.Finally, give s

First, what is an adornerAdorner, which is itself a function.The function of the adorner is to add some functionality to the existing function without changing its invocation mode, which is generally common.It is often used in scenarios where there is a need for facets, such as inserting logs, performance testing, transaction processing, caching, permission checking, and so on. (This quote: https://zhuanlan.zhihu.com/p/25648515)Second, the prerequisite knowledge of learning decorators1. function

. Original image2. HSV Space5. RGB Turn LabThe code is as follows:#encoding:utf-8import numpy as npimport cv2image = cv2.imread("H:\\img\\lena.jpg")cv2.imshow("Original",image)cv2.waitKey(0)#lab空间lab = cv2.cvtColor(image, cv2.COLOR_BGR2LAB)cv2.imshow("L*a*b*", lab)cv2.waitKey(0)The results are as follows1. Original image2. Lab Space Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced. Opencv-python