how to rename keyword argument of constructor by boost::python

Question

I have a C++ class like:

class Foo {
 public:
  Foo(int param1 = 0, int param2 = 1);
}

and I want to call it in python with keyword argument like below :

foo = Foo(arg1 = 1)

or

foo = Foo(arg2 = 5)

I don't know how to rename argument in constructor by boost::python , can anybody help me ? thank you in advance

Answer 1

To define the Python signature of your constructor with custom names and custom default values, you would export your class as follow:

boost::python::class_<Foo>(
    "Foo",
    boost::python::init<int, int>(
        (boost::python::arg("self"), boost::python::arg("arg1")=0, boost::python::arg("arg2")=1)
    )
);

Now from Python you would be able to do:

foo = Foo() # arg1 is 0, arg2 is 1
foo = Foo(1, 5) # arg1 is 1, arg2 is 5
foo = Foo(1) # arg1 is 1, arg2 is 1
foo = Foo(arg1=1) # arg1 is 1, arg2 is 1
foo = Foo(arg2=5) # arg1 is 0, arg2 is 5

Note: You do not have to declare the self parameter, but it improves the docstring of your constructor:

Foo.__init__( (object)self [, (int)arg1=0 [, (int)arg2=1]]) -> None

Which is useful if you use a documentation generator such as Sphinx, etc.