Raises exception if not exactly one item: Sequence unpacking: singleitem, = mylist # Identical in behavior (byte code produced is the same), # but arguably more readable since a lone trailing comma could be missed: [singleitem] = mylist Rampant insanity, unpack the input to the identity lambda function: # The only even semi-reasonable way to … Read more
My apologies for the length of this post, but I decided to opt for completeness. Once you know a few basic rules, it’s not hard to generalize them. I’ll do my best to explain with a few examples. Since you’re talking about evaluating these “by hand,” I’ll suggest some simple substitution rules. Basically, you might … Read more
You need to build a parameter pack of numbers and unpack them template<int …> struct seq { }; template<int N, int …S> struct gens : gens<N-1, N-1, S…> { }; template<int …S> struct gens<0, S…> { typedef seq<S…> type; }; // … void delayed_dispatch() { callFunc(typename gens<sizeof…(Args)>::type()); } template<int …S> void callFunc(seq<S…>) { func(std::get<S>(params) …); … Read more
The single star * unpacks the sequence/collection into positional arguments, so you can do this: def sum(a, b): return a + b values = (1, 2) s = sum(*values) This will unpack the tuple so that it actually executes as: s = sum(1, 2) The double star ** does the same, only using a dictionary … Read more