flatmap

来源： https://stackoverflow.com/questions/43995063/flatmap-on-dataframe

来源： https://stackoverflow.com/questions/63677178/sicp-ex2-41-map-and-flatmap

来源： https://stackoverflow.com/questions/63677178/sicp-ex2-41-map-and-flatmap

问题 How I can merge List<Map<String,String>> to Map<String,String> using flatMap ? Here's what I've tried: final Map<String, String> result = response .stream() .collect(Collectors.toMap( s -> (String) s.get("key"), s -> (String) s.get("value"))); result .entrySet() .forEach(e -> System.out.println(e.getKey() + " -> " + e.getValue())); This does not work. 回答1: Assuming that there are no conflicting keys in the maps contained in your list, try following: Map<String, String> maps = list.stream()

问题 According to the Mozilla Developer Website: The flatMap() method first maps each element using a mapping function, then flattens the result into a new array. It is identical to a map followed by a flat of depth 1, but flatMap is often quite useful, as merging both into one method is slightly more efficient. Example: let arr = [1, 2, 4, 2, 3, 3, 4, 5, 5, 5, 8, 8, 9, 10]; const flatMap = arr.flatMap(x => x); console.log(flatMap); TypeError: arr.flatMap() is not a function Why is this returning

问题 We have an array of the Person objects and each object has another array of String, which is optional. We want the consolidated list of car names in our society. struct Person { let name: String let address: String let age: Int let income: Double let cars: [String]? } let personsArray = [Person(name:"Santosh", address: "Pune, India", age:34, income: 100000.0, cars:["i20","Swift VXI"]), Person(name: "John", address:"New York, US", age: 23, income: 150000.0, cars:["Crita", "Swift VXI"]), Person

问题 given a list of documents, I want to obtain the pairs that shares at least one token. To do this I wrote the code below, that do that through an inverted index. object TestFlatMap { case class Document(id : Int, tokens : List[String]) def main(args: Array[String]): Unit = { val documents = List( Document(1, List("A", "B", "C", "D")), Document(2, List("A", "B", "E", "F", "G")), Document(3, List("E", "G", "H")), Document(4, List("A", "L", "M", "N")) ) val expectedTokensIds = List(("A",1), ("A"

问题 I'm working with an API of my own and a i'm hoping to chain a few paginated results using RxJava. I use cursor based pagination. (imagine there are 50 users in this first request): { "data":{ "status":"ok", "total":988, //users total "has_next_page":true, "end_cursor":"AQAxd8QPGHum7LSDz8DnwIh7yHJDM22nEjd", "users":[{"id":"91273813", "username":"codergirl", "full_name":"Code Girl", "picture_url":"https://cdn.com/21603182_7904715668509949952_n.jpg", }, ... ] } } Right now, I'm getting the first

问题 This is the sample example code in my book: from pyspark import SparkConf, SparkContext conf = SparkConf().setMaster("spark://chetan-ThinkPad- E470:7077").setAppName("FlatMap") sc = SparkContext(conf=conf) numbersRDD = sc.parallelize([1, 2, 3, 4]) actionRDD = numbersRDD.flatMap(lambda x: x + x).collect() for values in actionRDD: print(values) I am getting this error: TypeError: 'int' object is not iterable at org.apache.spark.api.python.PythonRunner$$anon$1.read(PythonRDD.scala:193) at org

问题 Consider the following code: typealias PersonRecord = [String : AnyObject] struct Person { let name: String let age: Int public init(name: String, age: Int) { self.name = name self.age = age } } extension Person { init?(record : PersonRecord) { guard let name = record["name"] as? String, let age = record["age"] as? Int else { return nil } self.name = name self.age = age } } Now I want to create an array of Person s from an array of Record s: let records = // load file from bundle let persons