function

问题 This question already has answers here : Filtering list of dataframes based on the number of observations in each dataframe (4 answers) Closed 1 year ago . Suppose I'm subsetting from a list of named data.frame s with respect to a subsetting variable called long . After subsetting, some data.frame s in the list may be empty because there is no match for subsetting in them. I was wondering how I could delete all such empty data.frame s in my final output. A simple example, and my unsuccessful

问题 When I try to view the built-in function all() in PyCharm, I could just see "pass" in the function body. How to view the actual implementation so that I could know what exactly the built-in function is doing? def all(*args, **kwargs): # real signature unknown """ Return True if bool(x) is True for all values x in the iterable. If the iterable is empty, return True. """ pass 回答1: Assuming you’re using the usual CPython interpreter, all is a builtin function object, which just has a pointer to

问题 When I try to view the built-in function all() in PyCharm, I could just see "pass" in the function body. How to view the actual implementation so that I could know what exactly the built-in function is doing? def all(*args, **kwargs): # real signature unknown """ Return True if bool(x) is True for all values x in the iterable. If the iterable is empty, return True. """ pass 回答1: Assuming you’re using the usual CPython interpreter, all is a builtin function object, which just has a pointer to

问题 I have the following code which defines a Car . Each Car has a color, along with a setColor(color) function. I want to add listener functions which are called whenever setColor(color) is called, and I want to be able to tack these listener functions on whenever I want. Is this a suitable approach? Is there a cleaner way? function Car() { this._color = 'red'; this._callbacks = {}; this.setColor = function(color) { this._color = color; console.log(">>> set car color to " + color); if (this.

问题 I want to call a function but depending on the situation I might call it with extra arguments or not. Here is a simple example: FUN <- function(arg1 = "default1", arg2 = "default2", arg3 = "default3") print(list(arg1, arg2, arg3)) x1 <- "hi" x2 <- TRUE x3 <- 1:3 use.arg3 <- FALSE # This will decide if `x3` is used or not. if (use.arg3) { FUN(arg1 = x1, arg2 = x2, arg3 = x3) } else { FUN(arg1 = x1, arg2 = x2) } While the code is clear, it feels a little redundant. Also imagine that if I had

问题 I want to store callbacks in a vector or another container in C++11. One way to do so would be to store a vector of std::function. This works well for lambda or std::bind with copyable arguments. However, if there is one non copyable (movable only) argument, it will fail due to the conversion from the lambda/std::bind internal type to the std::function... #include <vector> class NonCopyable { public: NonCopyable() = default; NonCopyable(const NonCopyable &) = delete; NonCopyable(NonCopyable &

问题 Lets take a veriable cars as an example. Cars has two columns cars$speed , cars$dist . I want to write a function that will print in one step summary for each column of a veriable(in this case cars). It would look like: f<-function(x){ #do some stuff } The result: name of first column: Min. 1st Qu. Median Mean 3rd Qu. Max. 4.0 12.0 15.0 15.4 19.0 25.0 name of second column: Min. 1st Qu. Median Mean 3rd Qu. Max. 2.00 26.00 36.00 42.98 56.00 120.00 How do I do that? 回答1: If all you want is a

问题 Can someone explain to me why JSLint complains about "Function inside the loop" with this example: for (var i = 0; i < buttons.length; i++) { (function(i) { buttons[i].onclick = function(e) { t.progressBars[t.current].update(buttons[i].getAttribute("data-value")); } })(i); } But dosen't when I change it to: function makeHandler(i) { return function() { t.progressBars[t.current].update(buttons[i].getAttribute("data-value")); } } for (var i = 0; i < buttons.length; i++) { buttons[i].onclick =

问题 I am looking to return a table of results from an Oracle function. Using a cursor would be easiest, but the application I have to work this into will not accept a cursor as a return value. The alternative is to create a type (likely wrapped in a package) to go along with this function. However, it seems somewhat superfluous to create several types (I have 4+ functions to write) just so I can return table results. Is there an alternative that I am missing? 回答1: UPDATE: See the first comment

问题 I am looking to return a table of results from an Oracle function. Using a cursor would be easiest, but the application I have to work this into will not accept a cursor as a return value. The alternative is to create a type (likely wrapped in a package) to go along with this function. However, it seems somewhat superfluous to create several types (I have 4+ functions to write) just so I can return table results. Is there an alternative that I am missing? 回答1: UPDATE: See the first comment