CPP_CHEN的专栏

Python Patterns - An Optimization AnecdotePython Patterns - An Optimization AnecdoteThe other day, a friend asked me a seemingly simple question: what's the best way to convert a list of integ

Python logging componentsLoggers expose the interface that application code directly uses.Handlers send the log records (created by loggers) to the appropriate destination.Filters provide a fine

MetaprogrammingMetaprogramming is the ability for a program to reason about itself or to modify.Metaprogramming is the writing of computer programs that write or manipulate other programs (o

Python Attributes and MethodsShalabh ChaturvediCopyright © 2005-2009 Shalabh ChaturvediAll Rights Reserved.About This BookExplains the mechanics of object attribute

----------------------Eggs and their Formats----------------------A "Python egg" is a logical structure embodying the release of aspecific version of a Python project, comprising its code,

Why so many Python web frameworks?When asked about the plethora of web frameworks for Python the answer is often that it is way too easy to put together one in Python. That certainly seems plaus

1) The "with" statementwith expr [as VAR]:    WITH-BLOCK"with" statement is something like "RAII" in C++, when "with" statement finishes, all resources will be cleaned automatically even there i

For example, code in the A.B.C module can do:from . import D                 # Imports A.B.Dfrom .. import E                # Imports A.Efrom ..F import G               # Imports A.F.G

1) Don't do trivial assignment in __init__ of the classDon't:class Foo(object):     def __init__(self):        self.attr1 = 0        self.attr2 = ''        self.attr3 = []        self.at

If you would like to improve the running performance of Python, try1) Use profile/cProfile to benchmark your program, find the possible hotspot, switch to correct data structure to solve problem etc

1) Everything is object in Python, even types (what the hell, how can this happen ? See below bullet points)2) "class" and "type" are the same thing, they are "type objects". "Type objects" can be s

Metaclass is class whichcreates other class (its instance is other class)Whenexecuting a class definition, the interpreter has to know the correct metaclass to use. It will lookfor a class attribute n

High Level FrameworkApplication Level Framework

1) pdb2) Winpdb3) pydev4) gdb python extentionReferences:https://code.google.com/p/winpdb/wiki/DebuggingTutorialhttp://stackoverflow.com/questions/132058/showing-the-stack-trace-from-a-r

One of the nicest features of the Data Model is the ability to override the behavior of rich comparison operators:import functools@functools.total_orderingclass Generic(object): def __ini

This is the second part of the talk I gave January 24, 2013 at the Ottawa Python Authors Group.Part One introduces Python iterables and iterators and generators. This part covers the advanced use

About PythonPython is an interpreted, object-oriented, high-level programming language with dynamic semantics. Its high-level built in data structures, combined with dynamic typing and dynamic b

A collection of not-so-obvious Python stuff you should know!I am really looking forward to your comments and suggestions to improve andextend this little collection! Just send

The Light and Dark sides of Python name bindingPosted on 2014-04-04, last modified 2014-04-09.What does bar.foo do? - An exploration of Python assignment, objects, attributes and descripto

OOP Concepts in Python 2.x - Part 1Published on: Mar 5th, 2014Tags: pythonPosted by Leonardo GiordaniAbstractObject-oriented programming (OOP) has been the leading programmin

OOP Concepts in Python 2.x - Part 2Published on: Mar 10th, 2014Tags: pythonPosted by Leonardo GiordaniAbstractThis post continues the analysis of the Python OOP implementatio

Default Parameter Values in PythonFredrik Lundh | July 17, 2008 | based on a comp.lang.python post(It happened to me in one of the first Python programs I ever wrote, and it took several yea

1) DefinitionAny new style class that implements at least one of those method is called a descriptor: __get__(self, object, type=None) -> value, __set__(self, obj, value) -> None, __delete__(self, o

Benchmark of Python WSGI ServersNicholas Piël | March 15, 2010It has been a while since the Socket Benchmark of Asynchronous server. That benchmark looked specifically at the raw socket perfor

Asynchronous Servers in PythonNicholas Piël | December 22, 2009There has already been written a lot on the C10K problem and it is known that the only viable option to handle LOTS of concurre

When a function has a "yield" expression, it is called generator.The generator doesn't run until it is called with next(g) or g.next(). The first time to call the function which has "yield" expression

Python Types and ObjectsShalabh ChaturvediCopyright © 2005-2009 Shalabh ChaturvediAll Rights Reserved.About This BookExplains Python new-style objects:what

1) DefinitionDecorator is actually a function, or more strictly is a callable. It acts like the "decorator" design pattern in a sense.2)  How to define a decorator and how to call the decora

iteration protocol: implement __iter__() methodsequence protocol ([]): implement __len__() and __getitem__() method with integer argument starting at 0iterator protocol: implement __next__() metho

After installing python2.6 32 bit and cx_Oracle5.1.2-11g.win32-py2.6.msi on XP system, try "import cx_Oracle", it reports "ImportError: DLL load failed: The specific module could not be found"Root c

cx_Oracle.connect throws "InterfaceError: Unable to acquire Oracle environment handle", it is the invalid "ORACLE_HOME" env variable which caused this problem in my case. After fix the ORACLE_HOME, ev

Note:1) When calling _buffer.popleft(), it doesn't hold any lock in QueueFeederThread.2) It uses semaphore/pipe for mulitiprocess resource management.3) Reader and Writer are holding different l

During the installation of package downloaded from sourceforge.net, it reports the following error in its post installation process.With the following traceback:Traceback (most recent call

In Python, how to explicitly free the non-trivial memory (not int/char/ etc) returned by C module ?Say C interface is like as below:____________________struct Dummy{    int a;    int b;

Python ctypes module is very convenient for python to integrate C module.Win7 X64 examples:1) Call c dll library passing in arguments and return structure ptrC lib:------------------------

Pythonic way to solve problems .1) Sort character in a strings = 'hello'''.join(sorted(s))2) Sort listtable = [(1, 'john', 23), \         (2, 'tom', 13), \         (3, 'lucy', 25), \

urllib/urllib2 in Python 2 have been cleaned up and consolidated in Python 3.Request submodule diagram

The Python installed is 64 bit 3.2.3 version. The Oracle XE database is 10g, 32 bit on 64 bit Windows server 2008.When trying to install Python 64 bit cx_Oracle module , it reports "import not a v

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Dictionary access in Python the right wayPosted by bluquar on 6 August 2013, 10:03 pmThe first step to writing good code is to read good code. The second step is to figure out what is wron