optional-arguments

In C++, can I have a defaulted argument to a function which defaults to __PRETTY_FUNCTION___ , ___FILE___ , and ___LINE__ as defined at the point of the caller and not the point the defaults are supplied in a header file without using macros? You can't, but you can acheive this behavior with an additional macro. For instance: #DEFINE THROW(e) throwException(e, __FILE__, __LINE__); On a side note, __PRETTY_FUNCTION__ is not standard. No. Macros are expanded at the source line where they occur. You probably can... but definitely not with the restriction you mentioned (no macros). 来源： https:/

I would like to have the following syntax: python utility.py file1 FILE1 file2 FILE2 where file1 and file2 are optional arguments. It is simple to make it working with this syntax: python utility.py --file1 FILE1 --file2 FILE2 using parser.add_argument('--file1',type=file) parser.add_argument('--file2',type=file) however, if I remove the dashes, argparse starts to interprete it as a positional rather than optional argument... In other words, is it possible to specifically tell argparse whether an argument is optional or positional so that I can have optional parameters without the dashes?

This question already has an answer here: “Least Astonishment” and the Mutable Default Argument 31 answers Python methods: default parameter values are evaluated ONCE 3 answers I put empty braces as the default value for an optional argument to a Python function, and pylint (using Sublime package) told me it was dangerous. Can someone explain why this is the case? And is a better alternative to use None instead? It's dangerous only if your function will modify the argument. If you modify a default argument, it will persist until the next call, so your "empty" dict will start to contain values

I'm using for the firs time optional arguments but I cannot understand difference between those two method definitions: private void method1([Optional, DefaultParameterValue(string.Empty)] string testString) { //do something } private void method2(string testString = "") { //do something } definition of method1 needs: using System.Runtime.InteropServices; Method2 definition is smaller and needs no import. Have I to consider something before using one of those method syntax? Method 1 was present since .NET 1.1. Method 2 was introduced with C# 4 (C# did not support optional parameters until then

I came across this today, and I am surprised that I haven't noticed it before. Given a simple C# program similar to the following: public class Program { public static void Main(string[] args) { Method(); // Called the method with no arguments. Method("a string"); // Called the method with a string. Console.ReadLine(); } public static void Method() { Console.WriteLine("Called the method with no arguments."); } public static void Method(string aString = "a string") { Console.WriteLine("Called the method with a string."); } } You get the output shown in the comments for each method call. I