dictionary

问题 After a couple hours of research (on MSDN websites and so on) I didn't manage to find out why the generic Dictionary<TKey, TValue> does not provide a ForEach() method like List<T> does. Could someone please give me an explanation? (I know that it's not hard to implement it as an extension method, a great example can be seen here, I just was wondering whether there might be a particular reason why it's not provided by the .NET libraries in the first place.) Thanks in advance. 回答1: Because it's

问题 I have a list that stores well over a million objects within it. I need to look through the list and update the objects found through the below query as efficiently as possible. I was thinking of using a Dictionary or HashSet, but I'm relatively new to C# and could not figure out how to implement these other two approaches. My current code is simply a LINQ statement searching through an IList. public IList<LandObject> landObjects = new List<LandObject>(); var lObjsToUpdate = from obj in

问题 I have the following list of dictionaries in python: data = [{'flag': 'one', 'timestamp': 20190710}, {'flag': 'one', 'timestamp': 20190711}, {'flag': 'two', 'timestamp': 20190712}, {'flag': 'two', 'timestamp': 20190709}] I would like to return the dictionary with the the highest value in the key timestamp and with the value one in the key flag . I have done something similar here: Return the key of the maximum value in a dictionary base on criteria in Python But cannot make it work in this

问题 Say I call map like this, using the anonymous closure argument $0 : array.map { return $0.description } How would I explicitly define that map returns a string ? This doesn’t work: array.map { -> String return $0.description } Contextual type for closure argument list expects 1 argument, which cannot be implicitly ignored Does that mean if I want to specify a return value I have to name my arguments? [EDIT: I know I do not need an explicit return type here; still would like how to specify one

问题 Is a Python dictionary thread safe when using the thread ID of the current thread only to read or write? Like import thread import threading class Thread(threading.Thread): def __init__(self, data): super(Thread, self).__init__() self.data = data def run(self): data = self.data[thread.get_ident()] # ... 回答1: If data is a standard Python dictionary, the __getitem__ call is implemented entirely in C, as is the __hash__ method on the integer value returned by thread.get_ident() . At that point

问题 I'm trying to serialize a dictionary in C#. All the examples I've been able to find create XML like the following: <Dictionary> <ArrayOfEntries> <Entry> <Key>myFirstKey</Key> <Value>myFirstValue</Value> </Entry> <Entry> <Key>mySecondKey</Key> <Value>mySecondValue</Value> </Entry> </ArrayOfEntries> </Dictionary> It varies, sometimes the ArrayOfEntries node isn't necessary, but I still see the regular pattern of the dictionary's key-value pairs being stored in their own nodes. What I would like

问题 I need to verify if another dict is a subset of another dict, there is a trick that in these dicts there are array of dict's. superset: dct_1 = { 'x': 'x', 'y': [ { 't': '123', 'a': 'a' } ] } subset: dict_2 = { 'x': 'x', 'y': [ { 't': '123' } ] } from Recursive function to check dictionary is a subset of another dictionary answer I get this error: TypeError: unhashable type: 'dict' My code: def is_subset(superset, subset): for key, value in subset.items(): if key not in superset: return False

问题 I'm just trying to read a .csv using the first row as keys for the dictionary, with no success. My file has two lines (test), items being delimited by tabs. subjectID logID logTimestamp gameKey userID writer gameTime gameCode gameDesc 9991 1711774 6/13/14 E9E91B56 L11-13 general 358 1002 GAMESCRIBE_CREATED Code : def process_data(file_path): users = {} # Open the .csv file and creates a dict of actions with open(file_path, 'rb') as csvfile: spamreader = csv.DictReader(csvfile, delimiter='\t')

问题 I read somewhere about other data structures similar to hashtables, dictionaries but instead of using ints, they were using floats/doubles, etc. Anyone knows what they are? 回答1: If you mean using floats/doubles as keys in your hash, that's easy. For example, in .NET, it's just using Dictionary<double,MyValueType> . If you're talking about having the hash be based off a double instead of an int.... Technically, you can have any element as your internal hash. Normally, this is done using an int

问题 I have the following json response from a flask application and am wondering how I can split it out into multiple "rows"/dicts. Output: {'class': [0.0, 1.0], 'probability': [0.8488858872836712, 0.1511141127163287]} What I desire is: [{"class": 0.0, "probability": 0.8488858872836712},{"class": 1.0, "probability": 0.1511141127163287}] I've tried something like the following but am not sure how to get both keys: {k: v for e in zip(model.classes_, probabilities[0]) for k, v in zip(('class',