How to use std::wstring in python

Question

Python is calling a C++ function (wrapped using swig).

C++:

  std::wstring getFilePathMultiByte();

I can call this function in python. Question is how do I use this returned wstring? want to append filename to this path which gives error as shown in output below.

Python:

  path = getFilePathMultiByte()
  print path, type(path)
  file = path + "/Information.log"

Output:

_2012ad3900000000_p_std__wstring, type 'SwigPyObject'
TypeError: unsupported operand type(s) for +: 'SwigPyObject' and 'str'

How do I create a std::wstring in python? That may allow concatenation for me.

Thanks.

Use type(path) to see available methods for an object. Also, pprint.pprint(path) will show you the attributes. — jordanm
– jordanm, Commented Aug 1, 2012 at 20:15

Flexo - Save the data dump · Accepted Answer · 2012-08-02 06:46:00Z

2

The following example worked as intended with SWIG 2.0 on my machine:

%module test

%include "std_wstring.i"

%inline %{
  std::wstring foo() {
    return L"hi";
  }
%}

Which I then tested with:

Python 2.7.3rc2 (default, Apr 22 2012, 22:30:17)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import test
>>> path = test.foo()
>>> print path, type(path)
hi <type 'unicode'>
>>> file = path + "/Information.log"
>>> print file
hi/Information.log
>>>

I'm not exactly sure what you've done wrong here - my guess would be you haven't got %include "std_wstring.i", but it's hard to say for certain given what you've shown.

edited Aug 2, 2012 at 6:46

answered Aug 1, 2012 at 21:01

Flexo - Save the data dump♦

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3 Comments

sambha Over a year ago

Thought I would get compile errors if proper includes are not present. I have %include "stl.i". Let me try this. BTW - What did type(path) print for you?

Flexo - Save the data dump Over a year ago

@sambha - the type was "<type 'unicode'>", but I'd marked it up wrongly in my original answer so it was being treated as HTML! As far as SWIG is concerned if it doesn't know enough about a type to wrap it properly it assumes the type is an opaque pointer and generates a wrapper accordingly.

sambha Over a year ago

Thanks. Adding %include "std_wstring.i" to the proper .i files solved it. Its unicode for me too. I have some chinese characters in the string so print is failing for other reasons. On to the next one. I had to edit <type aaa> in my question too.

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