python programming examples advanced

the recv () function, because the buffer has data, and the recv () function is generally not blocked.(3). This model is less used and belongs to the typical "pull model", where the upper-level application needs to call the recv () function to pull the data in.5. Asynchronous IO ModelThe asynchronous IO Model diagram is as follows:Description(1). The upper-level application calls the Aio_read function and submits an application-tier buffer to the kernel to write data to, and after the call is co

in class, so it is an error.Look again, the class with __getattr__:#!/usr/bin/python#-*-Coding:utf-8-*-Class Student (object):def __init__ (self):Self.name = ' Michael 'def __getattr__ (self, Other):If other== ' score ':Return 99s = Student ()Print S.namePrint S.score #Class中没有这个属性Print S.gg #Class中没有这个属性Look again, print's score and GG are not defined in class, but both have outputs. Because the program to find __getattr__, just well defined a chara

the input, you can see the bottleneck from different vision, as followsWhen the call data is determined to be high, and the season is much time, the function or method of the basking may have a loop that can try to optimize the otherWhen a function runs for a long time, the cache may be a good choice if possibleAnother good way to show bottlenecks from profiling data is to turn it into a chart and use the Gprof2dot tool (Http://code.google.comm/p/jrfonseca/wiki/Gprof2Dot) to present the profili

change the code in large quantities, so the implementation of the adorner decoratordef w1(func): def inner(): print("2222222222") func() return inner@w1 #相当于f1 = w1(f1)def f1(): print("f11111111")f1()输出：2222222222f11111111Multiple adornersdef makeBlod(fn): def wrapped(): print("11111111111") return "As you can see from the output below, when there are multiple adorners, the adorner runs from bottom to top输出：111111111112222222222233333333333General-Purpo

framework:Class User (Model): # Defines the property of the class to the column mapping id = integerfield (' id ') name = Stringfield (' username ') email = Stringfield (' E Mail ') password = Stringfield (' password ') # creates an instance of U = User (id = 123, name= ' Michael ', email= ' [email protected] ', pass word= ' My-pwd ') # Save to Database U.save ()Follow the above interface to implement the ORMClass Field (object): Def __init__ (self, Name, column_type): self.name = name Self.col

Iterators and generators are a topic that Python scholars often talk about and I can't mundane because it's worth summing up.IteratorsAn iterator is a tool that operates on an iterative object and spits out one element at a time through the next method. We used the for. In.. The internal use of iterators is the function of an iterator.If you want to customize an iterator class, you need to meet the following criteria: The __iter__ method need

underscores, as follows"""SqlitePostgresShal"""#如果它们实现一个协议, the Lib prefix is usually used, as followsImport Smtplib,urllib,telnetlib#它们在命名空间中也必须保持一致, this will be easier to use, as follows#from widgets.stringwidgets Import Textwidget Bad#from widgets.strings import Textwidget okay.#同样, you should always avoid using the same name as from the standard library module#当一个模块变得比较复杂, when there are many classes, it is a good practice to create a package and divide the module elements into other modul

typeerror:attempted to reuse key: ' A 'The value of a member is allowed to be duplicated, but is also the first member property when accessed, and Python considers the second member of the duplicate as the first alias from Import Enum class Book (Enum): = 1 = 1>>>book.abook.b #访问b也变成了打印a属性, B is treated as an alias of aIf the restriction enumeration is not duplicated, a unique module is introduced, and the unique is a class adorner, which is

0 and ') ... self._sc Ore = value ... >>> s=student () >>> s.set_score >>> s.score Traceback (most recent call Last): File " Attributeerror: ' Student ' object have no attribute ' score ' >>> S.get_score () >>> s.set_score Traceback (most recent call last): File File" Valueerror:value must between 0 and the Note! In this case, there is no way to protect data without an adorner. But with adorners, it's much easier to call a method into a property. >>> class Student2 (object):... @p

binding allows us to dynamically add functionality to class while the program is running, which is difficult to implement in a static language.But what if you really want to restrict the properties of an instance? Only add the name and age attributes to the student instance.For the purpose of limiting, Python allows you to define a special _slots_ variable when defining a class to limit the attributes that the class instance can add:>>classStudent (o

到正确的方法, as followsClass B (object):def _g (self):Return ' QQW 'def _g1 (self):Return Self._g ()Pr1=property (_G1)Class BB (B):def _get_price (self):Return ' BB 'CC=BB ()Print CC.PR1#QQW#尽管如此, most of the time attributes are added to the class to hide their properties, the methods that link to them are private, and all overloads are bad practices, in which case the overloaded properties themselves are better, as followsClass B (object):def _g (self):Return ' Q1QW 'P1=property (_g)Class BB (B):def

Tags: imp primary key self-increment make unified add primary key set screen enc Mysql SqlAlchemy Basic Steps 1.SqlAlchemy Basic structure syntax is as follows: Case: From SQLAlchemy import Create_engine,column,string,integer,foreignkey from sqlalchemy.ext.declarative Import Declarative_base from sqlalchemy.orm import sessionmaker,relationship import pymysql engine = Create_engine ("mysql+pymy Sql://chen:[emailprotected]:3306/school ", encoding= ' Utf-8 ', echo=true) #echo屏幕输出信息 S

):If OBJS in Cls._obj:Cls._obj.remove (OBJS)@classmethoddef not1 (cls,sub):Event=cls (sub)For O in Cls._obj:O (Event)#思路是观察者使用event类方法注册自己, and is obtained by carrying the event that triggers these events, as follows:Class Writevent (object):def __repr__ (self):Return ' writevent (self) 'Def log (event):print '%s:was writees '%event._objWritevent.reg (log)Class Anot (object):def __call__ (self, E):print ' Yean%s told me! ' %eWritevent.reg (Anot)WRITEVENT.NOT1 (' A given file ')#对这个实现, the follow

#-*-Coding:utf-8-*-# python:2.x__author__ = ' Administrator '# Explode code# Small is beautiful, this also applies to all levels of code, when a function, class or a code is too large, it should be decomposed# The contents of a function or a method should not play a screen, that is, about a line or so it will be difficult to track and understand# for code students you can see the Art of Unix programming

ensure that only a single instance exists in the current memory, avoiding memory waste!!!When you create an object, you can no longer use it directly: obj = Foo (), and you should call a special method: obj = Foo.dl ().The essence is actually to define a static method, to determine whether there is already a singleton object, if there is a direct return of the Singleton object, if not, create a singleton object, and then return to a single caseObjectThe last is the description of the special va

received your data! \ n'. Encode ('Utf-8')) - Else:Wuyi #indicates that the client is closed the client_dict[fd].close () - Wu Client_dict.popitem () - #need to cancel the event registered by the client About Epoll.unregister (FD) $ - #iterate through each client in the clients dictionary for the corresponding FD - forIteminchClient_dict.items (): - A

Specify Permissions GRANTS rights Table Operations Creating table Create tables Delete Table drop tables Clear Table Transcate Creating a temporary table create temporary table Automatic Incremental Auto INCREMENT Primary KEY PRIMARY Key FOREIGN Key FOREIGN Key Constraint CONSTRAINT ALTER TABLE Data manipulation New Data INSERT Deleting data Delete Updating Data Update WHERE JOIN GROUP by ORDER by INSERT

(Filename,mode), open (Filename1,mode1)) as (Reader,writer): writer.write ( Reader.read ())　　In Python 2.7 and later, it is replaced by a new syntax:With open (Filename,mode) as Reader,open (Filename1,mode1) as Writer: Writer.write (Reader.read ())　　5, Contextlib.closing ()The file class directly supports the context Manager API, but some objects that represent open handles are not supported, such as the object returned by Urllib.urlopen (). There

implement a __iter__ () method that returns an iterative object, and then the python for loop constantly calls the next () of the Iteration object. The Stopiteration method gets the next value of the loop until it exits the loop when it encounters an error.classFib (object):def __init__(self): SELF.A, self.b= 0, 1#Initialize two counters A, B def __iter__(self):returnSelf#The instance itself is an iterative object, so it returns itself defNext

return value must is a string object. Read the explanation, where to say is the user-oriented, and where the programmer???? See the bold word No, see the slide line has not??? It's all about acting for everyone!!! If you want to be in your own position, well, it seems like such a thing, it is really obscene and vague expression.Do not say, first small try:#!/usr/bin/python#-*-Coding:utf-8-*-Class Student (object):def __init__ (self, name):Self.hah