hashable

问题 Say I have a dictionary built like this: d={0:1, 1:2, 2:3, 10:4, 11:5, 12:6, 100:7, 101:8, 102:9, 200:10, 201:11, 202:12} and I want to create a subdictionary d1 by slicing d in such a way that d1 contains the following keys: 0, 1, 2, 100, 101, 102 . The final output should be: d1={0:1, 1:2, 2:3, 100:7, 101:8, 102:9} Is there an efficient Pythonic way of doing this, given that my real dictionary contains over 2,000,000 items? I think this question applies to all cases where keys are integers,

来源： https://stackoverflow.com/questions/57763416/swift-using-objectid-of-class-for-hashable-protocol-results-in-random-behaviour

来源： https://stackoverflow.com/questions/57763416/swift-using-objectid-of-class-for-hashable-protocol-results-in-random-behaviour

来源： https://stackoverflow.com/questions/57763416/swift-using-objectid-of-class-for-hashable-protocol-results-in-random-behaviour

来源： https://stackoverflow.com/questions/55687214/how-to-implement-hashinto-from-hashvalue-in-swift

问题 I have a method that takes (among others) a dictionary as an argument. The method is parsing strings and the dictionary provides replacements for some substrings, so it doesn't have to be mutable. This function is called quite often, and on redundant elements so I figured that caching it would improve its efficiency. But, as you may have guessed, since dict is mutable and thus not hashable, @functools.lru_cache can't decorate my function. So how can I overcome this? Bonus point if it needs

问题 I'm trying to get custom object which is hashable from UserDefault. My custom model is defined below: class WorkerProfileResponse: Mappable, Hashable{ static func == (lhs: WorkerProfileResponse, rhs: WorkerProfileResponse) -> Bool { return lhs.id == rhs.id } var hashValue: Int{ return self.id! } var id, loginStatus, lastLogin, lastActive: Int? var username, email, mobileNumber: String? var userCategories: [String]? var userSubCategories: [String]? var biometricToken: String? var accessToken:

问题 I'm reading Set You use a set instead of an array when you need to test efficiently for membership and you aren’t concerned with the order of the elements in the collection, or when you need to ensure that each element appears only once in a collection. Basically Set ensures uniqueness, it has some methods and relies on Hashable Use the contains(_:) method to test whether a set contains a specific element. Use the subtracting(_:) method to create a new set with the elements of a set that are

问题 I'm trying to make a dictionary with the key as a struct I've created and the value as an array of Ints. However, I keep getting the error: Type 'DateStruct' does not conform to protocol 'Hashable' I'm pretty sure I've implemented the necessary methods but for some reason it still doesn't work. Here's my struct with the implemented protocols: struct DateStruct { var year: Int var month: Int var day: Int var hashValue: Int { return (year+month+day).hashValue } static func == (lhs: DateStruct,

问题 I'm using sqlite file to get the diaryEntriesTeacher from the authorId. it generates the following object of authorId when I print the variable authorId is nil Code :- func applySelectQuery() { checkDataBaseFile() objFMDB = FMDatabase(path: fullPathOfDB) objFMDB.open() objFMDB.beginTransaction() do { let results = try objFMDB.executeQuery("select * from diaryEntriesTeacher", values: nil) while results.next() { let totalCount = results.resultDictionary let authorId = totalCount?["authorId"]!