comparison

问题 Can someone give me an explanation why isinstance() returns True in the following case? I expected False, when writing the code. print isinstance(True, (float, int)) True My guess would be that its Python's internal subclassing, as zero and one - whether float or int - both evaluate when used as boolean, but don't know the exact reason. What would be the most pythonic way to solve such a situation? I could use type() but in most cases this is considered less pythonic. 回答1: For historic

问题 Can someone give me an explanation why isinstance() returns True in the following case? I expected False, when writing the code. print isinstance(True, (float, int)) True My guess would be that its Python's internal subclassing, as zero and one - whether float or int - both evaluate when used as boolean, but don't know the exact reason. What would be the most pythonic way to solve such a situation? I could use type() but in most cases this is considered less pythonic. 回答1: For historic

问题 This very simple code: #include <iostream> using namespace std; void exec(char* option) { cout << "option is " << option << endl; if (option == "foo") cout << "option foo"; else if (option == "bar") cout << "opzion bar"; else cout << "???"; cout << endl; } int main() { char opt[] = "foo"; exec(opt); return 0; } generate two warning: comparison with string literal results in unspecified behaviour. Can you explain why exactly this code doesn't work, but if I change char opt[] to char *opt it

问题 I've got a double that prints as 0.000000 and I'm trying to compare it to 0.0f , unsuccessfully. Why is there a difference here? What's the most reliable way to determine if your double is zero? 回答1: To determine whether it's close enough to zero that it will print as 0.000000 to six decimal places, something like: fabs(d) < 0.0000005 Dealing with small inaccuracies in floating-point calculations can get quite complicated in general, though. If you want a better idea what value you've got,

问题 Is there something like startsWith(str_a, str_b) in the standard C library? It should take pointers to two strings that end with nullbytes, and tell me whether the first one also appears completely at the beginning of the second one. Examples: "abc", "abcdef" -> true "abcdef", "abc" -> false "abd", "abdcef" -> true "abc", "abc" -> true 回答1: Apparently there's no standard C function for this. So: bool startsWith(const char *pre, const char *str) { size_t lenpre = strlen(pre), lenstr = strlen

问题 There is probably a simple one-liner that I am just not finding here, but this is my question: How do I check if an ArrayList contains all of the objects in another ArrayList? I am looking (if it exists) for something along the lines of: //INCORRECT EXAMPLE: if(one.contains(two)) { return true; } else { return false; } For example: ArrayList one = {1, 2, 3, 4, 5} ArrayList two = {1, 2, 3} --> True ArrayList two = {} --> True ArrayList two = {1, 2, 3, 4, 5} --> True ArrayList two = {1, 5, 2} -

问题 Is there a way to compare how close two colors are to each other? If to say both of them are blue. At the moment the way that we compare them is to manually assign each possible color to a color family(red, green, blue...). And then just compare the strings :) But surely that manual task can be assigned to a neat little algorithm. 回答1: Delta-e, is a single number that represents the perceived 'distance' between two colors. The lower the number, the more similar the colors are to the human eye

问题 This question already has answers here : Java error: Comparison method violates its general contract (8 answers) Closed 6 years ago . Hi below is my compare method of my comparator. I am not sure what is wrong. I looked up other similar titled questions and answers on stack overflow but not sure what is wrong with my method but I keep getting java.lang.IllegalArgumentException: Comparison method violates its general contract! Any help will be greatly appreciated public int compare(Node o1,

问题 How can I test whether two JSON objects are equal in python, disregarding the order of lists? For example ... JSON document a : { "errors": [ {"error": "invalid", "field": "email"}, {"error": "required", "field": "name"} ], "success": false } JSON document b : { "success": false, "errors": [ {"error": "required", "field": "name"}, {"error": "invalid", "field": "email"} ] } a and b should compare equal, even though the order of the "errors" lists are different. 回答1: If you want two objects

问题 Consider the following snippet: int i = 99999999; byte b = 99; short s = 9999; Integer ii = Integer.valueOf(9); // should be within cache System.out.println(new Integer(i) == i); // "true" System.out.println(new Integer(b) == b); // "true" System.out.println(new Integer(s) == s); // "true" System.out.println(new Integer(ii) == ii); // "false" It's obvious why the last line will ALWAYS prints "false" : we're using == reference identity comparison, and a new object will NEVER be == to an