Added support for list insertion. (#1888)

include/pybind11/pytypes.h

@@ -1265,6 +1265,10 @@ public:
     template <typename T> void append(T &&val) const {
         PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
     }
+    template <typename T> void insert(size_t index, T &&val) const {
+        PyList_Insert(m_ptr, static_cast<ssize_t>(index),
+            detail::object_or_cast(std::forward<T>(val)).ptr());
+    }
 };
 
 class args : public tuple { PYBIND11_OBJECT_DEFAULT(args, tuple, PyTuple_Check) };

tests/test_pytypes.cpp

@@ -17,6 +17,8 @@ TEST_SUBMODULE(pytypes, m) {
         list.append("value");
         py::print("Entry at position 0:", list[0]);
         list[0] = py::str("overwritten");
+        list.insert(0, "inserted-0");
+        list.insert(2, "inserted-2");
         return list;
     });
     m.def("print_list", [](py::list list) {

tests/test_pytypes.py

@@ -9,14 +9,16 @@ from pybind11_tests import debug_enabled
 def test_list(capture, doc):
     with capture:
         lst = m.get_list()
-        assert lst == ["overwritten"]
+        assert lst == ["inserted-0", "overwritten", "inserted-2"]
 
         lst.append("value2")
         m.print_list(lst)
     assert capture.unordered == """
         Entry at position 0: value
-        list item 0: overwritten
-        list item 1: value2
+        list item 0: inserted-0
+        list item 1: overwritten
+        list item 2: inserted-2
+        list item 3: value2
     """
 
     assert doc(m.get_list) == "get_list() -> list"