copy

问题 My current implementation uses lots of copy constructors with this syntax MyClass::Myclass(Myclass* my_class) Is it really (functionnaly) different from MyClass::MyClass(const MyClass& my_class) and why? I was adviced that first solution was not a true copy constructor. However, making the change implies quite a lot of refactoring. Thanks!!! 回答1: It's different in the sense that the first isn't a copy constructor, but a conversion constructor. It converts from a MyClass* to a MyClass . By

问题 There are two data frames x, y . Id like to copy row with number J from X into Y. Something like Y[1,] <- X[j,] 回答1: Your example happens to pretty much answer your question. (Try it out!) If, instead of replacing a row in the target data.frame, you want to add a row to it, try rbind() instead: X <- data.frame(name=LETTERS[1:3], value=1:3, stringsAsFactors=FALSE) Y <- data.frame(name=letters[1:3], value=rnorm(3), stringsAsFactors=FALSE) X[1,] <- Y[1,] X <- rbind(X, Y[3,]) 来源： https:/

问题 Please, suggest me the best way of copying a folder from assets to /data/data/my_app_pkg/files. The folder from assets (www) contains files and subfolders. which I want to completely copy to the files/ of my internal app path mentioned. I am successfully able to copy a file from assets to internal app files/ path, but unable to do the same in case of copying folder, even assetmanager.list isn't helping me out, as it is copying only the files, but not the directories / subfolders. Please

问题 Is it possible to copy a module, and then make changes to the copy? To phrase another way, can I inherit from a module, and then override or modify parts of it? 回答1: To phrase another way, can I inherit from a module, and then override or modify parts of it? Yes. import module You can use stuff from module or override stuff in your script. You can also do this to create a "derived" module. Call this "module_2". from module import * Which imports everything. You can then use stuff from module

问题 I was wondering if there is an easy way in MATLAB to do the following operation: I'd like to copy a row or column of a matrix and insert it in the next row/column. For example: given a 3x3 matrix 1 2 3 4 5 6 7 8 9 I'd like to copy the first row and insert it as a second row: 1 2 3 1 2 3 4 5 6 7 8 9 Can someone advise how I could accomplish this in MATLAB? Thanks! 回答1: You can simply repeat the indices of the rows you'd like to repeat A = A([1 1 2 3],:) 回答2: To insert row number source as row

问题 I have a class object which contains a vector<unique_ptr> . I want a copy of this object to run non-const functions on. The original copy must remain const . What would the copy constructor for such a class look like? class Foo{ public: Foo(const Foo& other): ??? {} std::vector<std::unique_ptr> ptrs; }; 回答1: You cannot simply copy a std::vector<std::unique_ptr> because std::unique_ptr is not copyable so it will delete the vector copy constructor. If you do not change the type stored in the

问题 I'm trying to import data from a .csv file to Cassandra 3.2.1 via copy command.In the file are only 299 rows with 14 columns. I get the Error: Failed to import 299 rows: InvalidRequest - code=2200 [Invalid query] message="Batch too large" I used the following copy comand and tryied to increase the batch size: copy table (Col1,Col2,...)from 'file.csv' with delimiter =';' and header = true and MAXBATCHSIZE = 5000; I think 299 rows are not too much to import to cassandra or i am wrong? 回答1: The

问题 I would like to slice a DataFrame with a Boolean index obtaining a copy, and then do stuff on that copy independently of the original DataFrame. Judging from this answer, selecting with .loc using a Boolean array will hand me back a copy, but then, if I try to change the copy, SettingWithCopyWarning gets in the way. Would this then be the correct way: import numpy as np import pandas as pd d1 = pd.DataFrame(np.random.randn(10, 5), columns=['a', 'b', 'c', 'd', 'e']) # create a new dataframe

问题 I am working on a solution for technical drawings (svg/ruby). I want to manipulate rectangles, and have an add! method in this class: class Rect def add!(delta) @x1+=delta ... # and so on self end end I also need an add method returning a Rect , but not manipulating self : def add(delta) r=self.dup/clone/"copy" # <-- not realy the 3 and no quotes, just in text here r.add! delta end dup and clone don't do my thing but: def copy; Marshal.load(Marshal.dump(self)); end does. Why does such a basic

问题 I want to copy the contents of a DataGridView and paste it in Excel. I tried: myDataGrid.SelectAll(); DataObject dataObj = myDataGrid.GetClipboardContent(); Clipboard.SetDataObject(dataObj, true) But this just pastes nothing. Any suggestions? 回答1: Have you added this line? myDataGrid.ClipboardCopyMode = DataGridViewClipboardCopyMode.EnableWithoutHeaderText; Take a look at this MSDN article for a working sample. 回答2: If you use Microsoft Visual Studio You can do it in Design File. Your