Re: can't import most modules (but no exception)

[Barry S. <ba...@ba...>]

Py::Module canot import a module. It can only hold a ref to an already 
imported module.

Becuase of the complexity of import in python its easiest to use 
PyRun_SimpleString.

PyRun_SimpleString(  "import foo.bar" );

Barry
p.s. I did reply a while ago but sf.net's FUBAR dropped the mail.


On 01/07/2015 21:37, David Fox wrote:
> I’m trying to take the example from section 1.3 of the python 
> embedding documentation 
> (https://docs.python.org/3/extending/embedding.html#pure-embedding), 
> with usage
>
> Usage: call pythonfile funcname [args]
>
>
> and rewrite it using CXX (with some extra diagnostics, and modified to 
> use str() so it handles functions which return anything, not just long):
>
> #include <Python.h>
> #include <CXX/Objects.hxx>
> #include <string>
> #include <iostream>
>
> int
> main(int argc, char *argv[])
> {
>     int i;
>
>     if (argc < 3) {
>         fprintf(stderr,"Usage: call pythonfile funcname [args]\n");
>         return 1;
>     }
>
>     std::string name(argv[1]);
>
>     std::string funcname(argv[2]);
>     Py_Initialize();
>     std::string status;
>     try {
>         Py::Module module(name);
>
>         std::cout << module.repr() << '\n';
>         if (!module.isTrue()) {
>             std::cout << "module was null/false\n";
>             throw Py::Exception();
>         }
>         status = "finding function " + funcname;
>         if (!module.hasAttr(funcname)) {
>             std::cout << "function " << funcname + " not found\n";
>             throw Py::Exception();
>         }
>         Py::Object obj = module.getAttr(funcname);
>         if (!obj.isTrue()) {
>             std::cout << "function was null/false\n";
>             throw Py::Exception();
>         }
>         if (!obj.isCallable()) {
>             std::cout << "got function but not callable?\n";
>             throw Py::Exception();
>         }
>         status = "casting function " + funcname;
>         Py::Callable func(obj);
>         status = "creating arg tuple";
>         Py::Tuple fargs(argc - 3);
>         status = "filling arg tuple";
>         for (i = 0; i < argc - 3; ++i) {
>             fargs[i] = Py::Long(atoi(argv[i + 3]));
>         }
>         status = "calling";
>         Py::Object res(func.apply(fargs));
>         //        status = "converting to long";
>         //        Py::Long v(res);
>         std::cout << "Result of call: " << res.str() << '\n';
>     } catch (const Py::Exception &) {
>         std::cout << "call failed with status " << status << '\n';
>     }
>
>     Py_Finalize();
>     return 0;
> }
>
>
> The original version compiles and runs correctly.   For example
>
> $ ./call math exp 2
> Result of call: 7
>
> $ PYTHONPATH=`pwd` ./call multiply multiply 2 3
> Will compute 2 times 3
> Result of call: 6
>
> My CXX version works as long as the module I specify is sys or os:
>
> ./pure_cxx sys exc_info
>  <module 'sys' (built-in)>
>  Result of call: (None, None, None)
>
> $ ./pure_cxx os getcwd
> <module 'os' from 
> '/Library/Frameworks/Python.framework/Versions/3.4/lib/python3.4/os.py'>
> Result of call: /Users/dfox/python/test/embed
>
> but if I use math or a custom module, it fails to find the function in 
> the given module:
>
>     $ ./pure_cxx math exp 2
>     <module 'math'>
>     function exp not found
>     call failed with status finding function exp
>
>
>     $ PYTHONPATH=`pwd` ./pure_cxx multiply multiply 2 3
>     <module 'multiply'>
>     function multiply not found
>     call failed with status finding function multiply
>
>
> Oddly, it doesn’t raise an exception when I create the Py::Module, but 
> that module seems to be a dummy module, with the right name and a few 
> other attributes all with value None, as can be seen by converting the 
> module to a Py::List and iterating over it:
>
> 0  __name__ : math
>
> 1  __loader__ : None
>
> 2  __spec__ : None
>
> 3  __package__ : None
>
> 4  __doc__ : None
>
>
> Any idea what I’m doing wrong?
>
>
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