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- .. _type-conversions:
- Type conversions
- ################
- 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
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