optional-parameters

问题 Based on Disable global variable lookup in Python (and my own answer there), I have had problems when using a function with optional parameters such as in this minimal example: import types def noglobal(f): return types.FunctionType(f.__code__, {}) @noglobal def myFunction(x=0): pass myFunction() Essentially, it fails like this: Traceback (most recent call last): File "SetTagValue.py", line 10, in <module> myFunction() TypeError: myFunction() missing 1 required positional argument: 'x' Why is

问题 It's just, why do this: find([spec=None[, fields=None[, skip=0[, limit=0[, timeout=True[, snapshot=False[, tailable=False[, sort=None[, max_scan=None[, as_class=None[, slave_okay=False[, await_data=False[, partial=False[, manipulate=True[, read_preference=ReadPreference.PRIMARY[, exhaust=False[, compile_re=True[, **kwargs]]]]]]]]]]]]]]]]]]) Which seems ugly and confusing, yet appears in every api docs I've ever come across, I may lack some basic python knowledge. 回答1: I do not have any

问题 i want to know how to use: string limit = WebOperationContext.Current.IncomingRequest.UriTemplateMatch.QueryParameters["Limit"]; in my wcf in this method: CityNewsList GetNewsByCity(string DeviceType,string id,string limit); here 'devicetype' and 'id' are default parameter and what i want is 'limit' as optional parameter means user have a choice to pass this parameter he can pass or can not pass this. want to use limit as: if (limit == some value) { //do this. } if (limit == null) { // do

问题 In my SELECT statement i use optional parameters in a way like this: DECLARE @p1 INT = 1 DECLARE @p2 INT = 1 SELECT name FROM some_table WHERE (id = @p1 OR @p1 IS NULL) AND (name = @p2 OR @p2 IS NULL) In this case the optimizer generates "index scan" (not seek) operations for the entity which is not most effective when parameters are supplied with not null values. If i add the RECOMPILE hint to the query the optimizer builds more effective plan which uses "seek". It works on my MSSQL 2008 R2

问题 I'm currently looking into Scheme, and the way I have understood it, procedures can take an arbitrary number of arguments. I have been trying to play around with this, but I'm struggling to grasp the concept. For instance, say I want to write a welcome message, based on information provided by the user. If user provides a first and last name, the program shout write: Welcome, <FIRST> <LAST>! ;; <FIRST> = "Julius", <LAST>= "Caesar" Welcome, Julius Caesar! Otherwise, the program should refer to

问题 I was wondering about providing backwards compatibility by using optional parameters. In my program I have an interface with a function that is used throughout my program as well as in a lot of unittests. For some new functionality, a boolean has to be passed into this function which will alter its behaviour if set to false . If you pass in true , you will get the same behaviour as before. Now I have to pass in true everywhere where in my current code where I have called this function before.

问题 I'm trying to pass an optional argument to a geometry function, called offset , which may or may not be specified, but C# doesn't allow me to do any of the following. Is there a way to accomplish this? Null as default Error: A value of type '' cannot be used as a default parameter because there are no standard conversions to type 'System.Drawing.Point' public void LayoutRelative(.... Point offset = null) {} Empty as default Error: Default parameter value for 'offset' must be a compile-time

问题 I have a (legacy) VB6 program that needs some work. I have a stored procedure that updates a table of vendors. In this particular form, I don't need to update the entire row, just 10 or so columns out of the 20ish. Here is some pseudo code that works fine if I want to update the entire row: CREATE PROCEDURE [dbo].[spUpdateVendor]( @pID INT, @pVendorID varchar(254), @pVendorName varchar(255), @pContact varchar(255), @pEmail varchar(255), ...) AS BEGIN SET NOCOUNT ON; SET XACT_ABORT ON DECLARE

问题 I am trying to write a genetic algorithm for homework to solve the travelling salesman problem. One of the mutation functions that I'm trying is to use random.shuffle on the tour. When I read the documentation for random.shuffle , I see: shuffle(self, x, random=None, int=<type 'int'>) method of random.Random instance x, random=random.random -> shuffle list x in place; return None. Optional arg random is a 0-argument function returning a random float in [0.0, 1.0); by default, the standard

问题 If I have the following method in Ruby: def foo(arg1, arg2 = "bar") puts arg1 puts arg2 end Is there a way of determining if a user passed a value in for arg2 within the method? Obviously I could just add if arg2 == "bar" to the method, but this doesn't catch the case where the user manually passed in "bar" herself. Of course, I could set the default to be something that no user would ever pass in, but then that gets pretty ugly pretty quickly. Is there anything elegant out there? 回答1: I am