Method zip

src/main/java/net/starlark/java/eval/MethodLibrary.java:978–1014

(Sequence<?> args, StarlarkThread thread)

  }

  @StarlarkMethod(
      name = "zip",
      doc =
          "Returns a <code>list</code> of <code>tuple</code>s, where the i-th tuple contains "
              + "the i-th element from each of the argument sequences or iterables. The list has "
              + "the size of the shortest input. With a single iterable argument, it returns a "
              + "list of 1-tuples. With no arguments, it returns an empty list. Examples:"
              + "<pre class=\"language-python\">"
              + "zip()  # == []\n"
              + "zip([1, 2])  # == [(1,), (2,)]\n"
              + "zip([1, 2], [3, 4])  # == [(1, 3), (2, 4)]\n"
              + "zip([1, 2], [3, 4, 5])  # == [(1, 3), (2, 4)]</pre>",
      extraPositionals = @Param(name = "args", doc = "lists to zip."),
      useStarlarkThread = true)
  public StarlarkList<?> zip(Sequence<?> args, StarlarkThread thread) throws EvalException {
    StarlarkList<Tuple> result = StarlarkList.newList(thread.mutability());
    int ncols = args.size();
    if (ncols > 0) {
      Iterator<?>[] iterators = new Iterator<?>[ncols];
      for (int i = 0; i < ncols; i++) {
        iterators[i] = Starlark.toIterable(args.get(i)).iterator();
      }
      rows:
      for (; ; ) {
        Object[] elem = new Object[ncols];
        for (int i = 0; i < ncols; i++) {
          Iterator<?> it = iterators[i];
          if (!it.hasNext()) {
            break rows;
          }
          elem[i] = it.next();
        }
        result.addElement(Tuple.wrap(elem));
      }
    }
    return result;
  }

  /** Starlark bool type. */
  @StarlarkBuiltin(