Boost C++ Libraries

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Boost.Python

Header <boost/python/enum.hpp>

Contents

Introduction
Classes
Class template enum_
Class template enum_ synopsis
Class template enum_ constructors
Class template enum_ modifier functions
Example(s)

Introduction

<boost/python/enum.hpp> defines the interface through which users expose their C++ enumeration types to Python. It declares the enum_ class template, which is parameterized on the enumeration type being exposed.

Classes

Class template enum_<T>

Creates a Python class derived from Python's int type which is associated with the C++ type passed as its first parameter.

Class template enum_ synopsis

namespace boost { namespace python
{
  template <class T>
  class enum_ : public object
  {
    enum_(char const* name);
    enum_<T>& value(char const* name, T);
    enum_<T>& export_values();
  };
}}

Class template enum_ constructors

enum_(char const* name);
Requires: name is an ntbs which conforms to Python's identifier naming rules.
Effects: Constructs an enum_ object holding a Python extension type derived from int which is named name. The named attribute of the current scope is bound to the new extension type.

Class template enum_ modifier functions

inline enum_<T>& value(char const* name, T x);
Requires: name is an ntbs which conforms to Python's identifier naming rules.
Effects: adds an instance of the wrapped enumeration type with value x to the type's dictionary as the named attribute
.
Returns: *this
inline enum_<T>& export_values();
Effects: sets attributes in the current scope with the same names and values as all enumeration values exposed so far by calling value()
.
Returns: *this

Example(s)

C++ module definition

#include <boost/python/enum.hpp>
#include <boost/python/def.hpp>
#include <boost/python/module.hpp>

using namespace boost::python;

enum color { red = 1, green = 2, blue = 4 };

color identity_(color x) { return x; }

BOOST_PYTHON_MODULE(enums)
{
    enum_<color>("color")
        .value("red", red)
        .value("green", green)
        .export_values()
        .value("blue", blue)
        ;
    
    def("identity", identity_);
}

Interactive Python:

>>> from enums import *

>>> identity(red)
enums.color.red

>>> identity(color.red)
enums.color.red

>>> identity(green)
enums.color.green

>>> identity(color.green)
enums.color.green

>>> identity(blue)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
NameError: name blue' is not defined

>>> identity(color.blue)
enums.color.blue

>>> identity(color(1))
enums.color.red

>>> identity(color(2))
enums.color.green

>>> identity(color(3))
enums.color(3)

>>> identity(color(4))
enums.color.blue

>>> identity(1)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: bad argument type for built-in operation

Revised 13 December, 2002

© Copyright Dave Abrahams 2002.