tuples

问题 I have a piece of code as below: tupvalue = [('html', 96), ('css', 115), ('map', 82)] So while printing the above tuple in the desired format for a particular index I found a code like this: >>> '%s:%d' % tupvalue[0] 'html:96' I'm wondering how the single value tupvalue[0] is recognised as a tuple of two values by the format specifier '%s:%d' ? Please explain this mechanism with a documentation reference. How can I use a comprehension to format all the values in tupvalue in the required

问题 At this answer here on SO, there's a comment suggesting a useful C++ construct, similar to make_zip_iterator , but for ranges: It takes a tuple of ranges and produces a new range - whose begin() and end() iterators are the appropriate zip iterators. Now, this should not be too difficult to implement, but I was wondering - Isn't already offered already by Boost somehow? 回答1: Boost.Range is providing combine() function as zip_iterator 's range. http://www.boost.org/doc/libs/1_56_0/libs/range

问题 I need to write a function to convert tuple to byte array. The type of tuple may include int, long, double, std::string, char* ,etc. The size and type of tuple are arbitrary, such as std:tuple<string, int, double> t1("abc", 1, 1.3); or std:tuple<char*, int, int, float, double, string> t2("abc", 1, 2, 1.3, 1.4, "hello"); I want use these tuple as input, and the byte array as return value. What should I do ? 回答1: There is also the brilliant C++ API for message pack which supports tuples

问题 I'm trying to make a call to a templated function like this : typedef std::tuple<int, double, bool> InstrumentTuple; Cache cache; InstrumentTuple tuple = cache.get<InstrumentTuple>(); I know I could "simply" pass the types of the tuple. This is what I do know but it is quite cumbersome since I make a lot of calls to this function and since the tuples are quite long: InstrumentTuple tuple = c.get<int, double, bool>(); // syntax I'd like to avoid So I tried multiple implementations of the get

问题 Given a list of tuples like so: a = [ ( "x", 1, ), ( "x", 2, ), ( "y", 1, ), ( "y", 3, ), ( "y", 4, ) ] What would be the easiest way to filter for unique first element and merge the second element. An output like so would be desired. b = [ ( "x", 1, 2 ), ( "y", 1, 3, 4 ) ] Thanks, 回答1: You can use a defaultdict: >>> from collections import defaultdict >>> d = defaultdict(tuple) >>> a = [('x', 1), ('x', 2), ('y', 1), ('y', 3), ('y', 4)] >>> for tup in a: ... d[tup[0]] += (tup[1],) ... >>>

问题 A similar question was asked Parameterised Modules in Erlang, it is about "what". My question is about "why"? OTP Technical Board - Decisions affecting R16 contains the board decision about this issue, but I don't know the reason behind the decision. Stateful Module in Programming Erlang 2ndEdition by Joe Armstrong introduces this feature in detail, but I don't see the author's attitude. If we read the official document Function Calls, we see this feature is deliberately skimmed. In fact, the

问题 Given a variadic template Types... , I would like to store A<> for each of the types in the pack. This could be done in a tuple of A<> 's, but I'd need to programmatically derive the type of said tuple. Is such a thing even possible in c++11/14/17? template <class T> class A { }; template <class... Types> class B { // A tuple of A<>'s for each type in Types... std::tuple<A<Type1>, A<Type2>, ...> data; }; 回答1: Simply with: template <class... Types> class B { std::tuple<A<Types>...> data; }; 来源

问题 I'm trying to solve a new program with Prolog, and I'm stuck, and don't know how to continue... I must do a predicate that has 3 arguments, the first is a list of elements, the second one is a list of tuples, and the third one must be a list returned that contains the second element of the tuples, if the first element of the tuple match with an element of the first argument list. It must delete copies also!! For example, check([a,c],[(a,aa),(bb,bbb),(a,aa),(c,def)],X). X = [aa, def] . As you

问题 How can I turn this: students = [("Abe", 200), ("Lindsay", 180), ("Rachel" , 215)] into this: Abe 200 Lindsay 180 Rachel 215 EDIT: This should be able to work for any size list. 回答1: Use string formatting: >>> students = [("Abe", 200), ("Lindsay", 180), ("Rachel" , 215)] >>> for a, b in students: ... print '{:<7s} {}'.format(a, b) ... Abe 200 Lindsay 180 Rachel 215 回答2: Use rjust and ljust: for s in students: print s[0].ljust(8)+(str(s[1])).ljust(3) Output: Abe 200 Lindsay 180 Rachel 215 回答3:

问题 I have a list of nested tuples of the form: [(a, (b, c)), ...] Now I would like to pick the element which maximizes a while minimizing b and c at the same time. For example in [(7, (5, 1)), (7, (4, 1)), (6, (3, 1))] the winner should be (7, (4, 1)) Any help is appreciated. 回答1: In my understanding, you want to sort decreasingly by a, and ascendingly by b, then by c. If that's right, you can do it like so: >>> l=[(7, (5, 1)), (7, (4, 1)), (6, (3, 2)), (6, (3, 1))] >>> sorted(l, key = lambda x: