Type conversions

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Apart from enabling cross-language function calls, a fundamental problem

that a binding tool like pybind11 must address is to provide access to

native Python types in C++ and vice versa. There are three fundamentally

different ways to do this—which approach is preferable for a particular type

depends on the situation at hand.

1. Use a native C++ type everywhere. In this case, the type must be wrapped

   using pybind11-generated bindings so that Python can interact with it.

2. Use a native Python type everywhere. It will need to be wrapped so that

   C++ functions can interact with it.

3. Use a native C++ type on the C++ side and a native Python type on the

   Python side. pybind11 refers to this as a *type conversion*.

   Type conversions are the most "natural" option in the sense that native

   (non-wrapped) types are used everywhere. The main downside is that a copy

   of the data must be made on every Python ↔ C++ transition: this is

   needed since the C++ and Python versions of the same type generally won't

   have the same memory layout.

   pybind11 can perform many kinds of conversions automatically. An overview

   is provided in the table ":ref:`conversion_table`".

The following subsections discuss the differences between these options in more

detail. The main focus in this section is on type conversions, which represent

the last case of the above list.

.. toctree::

   :maxdepth: 1

   overview

   strings

   stl

   functional

   chrono

   eigen

   custom