思考1 char str1[]=\"abc\";与char *str2=\"abc\";的区别
char str1[]="abc"//栈 char *str2="abc"//abc\0在常量区，str2在栈上 来源： https://www.cnblogs.com/epll/p/11386189.html
abc
How would I implement a dict with Abstract Base Classes in Python? [duplicate]
This question already has an answer here: How to “perfectly” override a dict? 5 answers I attempted to implement a mapping in Python by using the abstract base class, MutableMapping, but I got an error on instantiation. How would I go about making a working version of this dictionary that would emulate the builtin dict class, in as many ways as possible, to be clear, with Abstract Base Classes ? >>> class D(collections.MutableMapping): ... pass ... >>> d = D() Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: Can't instantiate abstract class D with abstract
Path类与Directory类与File类
Path 对路径 字符串进行操作 获得后缀 能合并路径 获取文件名 Directory和DirectoryInfo 对目录进行操作 判断目录是否存在 创建目录 删除目录 获取目录下所有的子目录 获取目录下所有的子文件 File和FileInfo 对文件进行操作 读文件 写文件 追加文件 判断文件是否存在 创建文件 删除文件 1、Path类 View Code using System; using System.IO;//目录和文件操作的名称空间 namespace _11_Path类 { class Program { static void Main(string[] args) { string path = "c:\\abc\\1.txt" ; //注意这里是对路径字符串的操作 而不是真正的文件 “修改”支持字符串层面的，没有真的给文件改名 path = Path.ChangeExtension(path, "avi" );//ChangeExtension()修改文件后缀名1.avi c:\\abc\\1.avi //将两个路径合成一个路径，比用+好，可以方便解决是不是加斜线的问题，自动处理路径分隔符的问题 path = Path.Combine("c:\\abc\\def\\" , "1.jpg"); //c:\abc\def\1.jpg //得到文件所在文件夹的位置
Python different behaviour with abstractmethod
问题 I have two classes inheriting from the same parent P : from abc import ABCMeta, abstractmethod class P(object): __metaclass__ = ABCMeta @abstractmethod def foo(self): pass class C(P): pass class D(tuple, P): pass The only difference is that D inherited from tuple and P while C inherits from P only. Now this is the behavior: c = C() got error, as expected: TypeError: Can't instantiate abstract class C with abstract methods foo but d = D() works without error! I can even call d.foo() . How can
Python - Testing an abstract base class
问题 I am looking for ways / best practices on testing methods defined in an abstract base class. One thing I can think of directly is performing the test on all concrete subclasses of the base class, but that seems excessive at some times. Consider this example: import abc class Abstract(object): __metaclass__ = abc.ABCMeta @abc.abstractproperty def id(self): return @abc.abstractmethod def foo(self): print "foo" def bar(self): print "bar" Is it possible to test bar without doing any subclassing?
How would I implement a dict with Abstract Base Classes in Python? [duplicate]
问题 This question already has an answer here: How to “perfectly” override a dict? 5 answers I attempted to implement a mapping in Python by using the abstract base class, MutableMapping, but I got an error on instantiation. How would I go about making a working version of this dictionary that would emulate the builtin dict class, in as many ways as possible, to be clear, with Abstract Base Classes ? >>> class D(collections.MutableMapping): ... pass ... >>> d = D() Traceback (most recent call last
单例模式
#import " Abc.h " @implementation Abc + (Abc * )sharedInstance { static Abc *abc = nil; static dispatch_once_t onceToken; dispatch_once( &onceToken, ^ { abc = [[Abc alloc] init]; }); return abc; } @end 这是Objective-c的singleton写法。 转载于:https://www.cnblogs.com/mystory/archive/2013/02/18/2915859.html 来源： https://blog.csdn.net/weixin_30287169/article/details/99019307
Why use Abstract Base Classes in Python?
Because I am used to the old ways of duck typing in Python, I fail to understand the need for ABC (abstract base classes). The help is good on how to use them. I tried to read the rationale in the PEP , but it went over my head. If I was looking for a mutable sequence container, I would check for __setitem__ , or more likely try to use it ( EAFP ). I haven't come across a real life use for the numbers module, which does use ABCs, but that is the closest I have to understanding. Can anyone explain the rationale to me, please? Oddthinking Short version ABCs offer a higher level of semantic