The comment by @user2357112 that this seems to be coincidence appears to be correct. The relevant part of the Python source code is in Python/ast.c: switch (e->kind) { # several cases snipped case List_kind: e->v.List.ctx = ctx; s = e->v.List.elts; break; case Tuple_kind: if (asdl_seq_LEN(e->v.Tuple.elts)) { e->v.Tuple.ctx = ctx; s = e->v.Tuple.elts; } else { … Read more
In php5.6 Argument unpacking via … (splat operator) has been added. Using it, you can get rid of call_user_func_array() for this simpler alternative. For example having a function: function add($a, $b){ return $a + $b; } With your array $list = [4, 6]; (after php5.5 you can declare arrays in this way). You can call … Read more
You can’t do that directly, but it isn’t terribly difficult to write a utility function to do this: >>> def unpack_list(a, b, c, *d): … return a, b, c, d … >>> unpack_list(*range(100)) (0, 1, 2, (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, … Read more
According to PEP-0526, you should annotate the types first, then do the unpacking a: int b: int a, b = t
d2, = values[s] is just like a,b=f(), except for unpacking 1 element tuples. >>> T=(1,) >>> a=T >>> a (1,) >>> b,=T >>> b 1 >>> a is tuple, b is an integer.
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 could google “tuple unpacking”. This can be used in various places in Python. The simplest is in assignment: >>> x = (1,2) >>> a, b = x >>> a 1 >>> b 2 In a for-loop it works similarly. If each element of the iterable is a tuple, then you can specify two variables, … Read more
Python separates the right-hand side expression from the left-hand side assignment. First the right-hand side is evaluated, and the result is stored on the stack, and then the left-hand side names are assigned using opcodes that take values from the stack again. For tuple assignments with 2 or 3 items, Python just uses the stack … 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