How can I make SWIG return unicode objects for strings in Python 2?

Question

I have something like the following:

swigtest.cpp

#include <string>

class Foo {
public:
    std::string bar() {
        return "baz";
    }
};

inline Foo* new_foo() {
    return new Foo;
}

swigtest.i

%module swigtest
%{
#include "swigtest.hpp"
%}

%include <std_string.i>
%include "swigtest.hpp"

%newobject new_foo;

useswig.py

from swigtest import new_foo

foo = new_foo()
print(foo.bar())
print(type(foo.bar()))

$ swig -c++ -python -modern swigtest.i
$ g++ -fpic -shared -I/usr/include/python2.7 -DSWIG_PYTHON_2_UNICODE swigtest_wrap.cxx -lpython2.7 -o _swigtest.so
$ python2 useswig.py
baz
<type 'str'>

Is there any way to get that to output

<type 'unicode'>

instead? I understand from the docs that

When the SWIG_PYTHON_2_UNICODE macro is added to the generated code ... Unicode strings will be successfully accepted and converted from UTF-8, but note that they are returned as a normal Python 2 string

Is there a way to achieve that, possibly with a custom typemap somehow?

Thank you for an good MCVE. I had to tweak it slightly for Windows, but still +1. — Mark Tolonen
– Mark Tolonen, Commented Feb 10, 2017 at 2:57

Mark Tolonen · Accepted Answer · 2017-02-10 02:55:17Z

2

A custom typemap works, but you'll need more to handle input parameters, output arguments, etc.

%module swigtest
%{
#include "swigtest.hpp"
%}

//%include <windows.i>  // Need for Windows DLLs to handle __declspec(dllexport)
//%include <std_string.i>
%typemap(out) std::string %{
    $result = PyUnicode_FromString($1.c_str());
%}

%include "swigtest.hpp"

%newobject new_foo;

Output:

C:\test>py -2 useswig.py
baz
<type 'unicode'>

answered Feb 10, 2017 at 2:55

Mark Tolonen

181k26 gold badges182 silver badges278 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Tavian Barnes Over a year ago

Great! If I'm using the same .i for multiple language bindings, how can I make that typemap only apply to Python?

Mark Tolonen Over a year ago

@TavianBarnes Sure, #ifdef SWIGPYTHON around it. Other languages are listed in the documentation.

Collectives™ on Stack Overflow

How can I make SWIG return unicode objects for strings in Python 2?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related