Problem getting stdout redirected for embedded Python

[eliot.muir at interfaceware.com]

Hmmm,

Well setting the LocalDict to be equal to the GlobalDict
eliminated the problem.  I got the idea from looking at the
PyRun_SimpleString code.  I'd still appreciate it if someone
could explain what the difference is between these two dictionaries
and why one might want them to be distinct.

Cheers,
Eliot


In article <8sq1t2$hhm$1 at nnrp1.deja.com>,
  eliot.muir at interfaceware.com wrote:
> Hi,
>
> I've been trying to embedd Python in a C application
> and come to the standard problem of how to redirect the
> stdout and stderr.
>
> The approach of creating an object which implements the write command
> and assigning it to the sys.stderr and sys.stdout seems to be the
> right approach.  But I found that I seem to running into some
> name scoping problems.  I believe it is something to do with the
> way I am invoking Python using the C API.
>
> I spent half an hour stripping everything down to the most basic
> code which reproduces the problem.  This script works when invoked
> from the python interpreter:
>
> import string
> print string.lower("LOWERCASE")
> class myRedirect:
>    def write(self, str):
>       print string.lower(str)
> a = myRedirect()
> a.write("LOWERCASE")
>
> Run as a script it predictably produces the output "lowercase" twice.
>
> But embedded in my C program the script fails on the last line with
the
> statment "There is no variable string" indicating some type of scoping
> problem.
>
> This is the complete C code:
>
> #include <Python.h>
>
> int main()
> {
>    Py_Initialize();
>    PyObject* main_module, *GlobalDict, *LocalDict;
>    main_module = PyImport_ImportModule ("__main__");
>    GlobalDict = PyModule_GetDict(main_module);
>    LocalDict = PyDict_New();
>    Py_XDECREF(main_module);
>
>    PyRun_String("import string\n", Py_file_input, GlobalDict,
> LocalDict);
>    if (NULL == PyRun_String("print string.lower(\"LOWERCASE\")\n",
> Py_file_input, GlobalDict, LocalDict))
>    {
>       PyErr_Print();
>    }
>    if (NULL == PyRun_String("class myRedirect:\n   def write(self,
> str):\n      print string.lower(\"LOWERCASE\")\n", Py_file_input,
> GlobalDict, LocalDict))
>    {
>       PyErr_Print();
>    }
>    if (NULL == PyRun_String("a = myRedirect()\n", Py_file_input,
> GlobalDict, LocalDict))
>    {
>       PyErr_Print();
>    }
>    if (NULL == PyRun_String("a.write(\"LOWERCASE\")\n", Py_file_input,
> GlobalDict, LocalDict))
>    {
>       PyErr_Print();
>    }
>    Py_XDECREF(LocalDict);
>    Py_XDECREF(GlobalDict);
>
> 	Py_Exit(0);
>    return 0;
> }
>
> I suspect it has to with my lack of understanding of the global
> and local name space dictionary arguments?
>
> Any suggestions appreciated!
>
> Cheers,
> Eliot
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>


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