Embedding, "import site", PYTHONHOME, and an old, old issue

[Jim Hill]

Well, I've found about a hundred thousand web pages where people have
had the same problem I have but nary a page with a solution that works
for me.

I want to do a simple embed, so I've followed the example in the
Extending and Embedding documentation:

In the .c file,

#include <Python.h>

int routine() {
Py_Initialize();
PyRun_SimpleString("from time import time,ctime\n"
"print 'Today is',ctime(time())\n");
Py_Finalize();
return 0;
}

The code compiles just fine, but when I execute it the call to
Py_Initialize() comes back with:

'import site' failed; use -v for traceback
Traceback (most recent call last):
File "<string>", line 1, in <module>
ImportError: No module named time



I found a lot of websites that say to set PYTHONHOME to the the path to
the directory where site.py lives. I did that but I get the same error.

Here are a few bits o' additional information:

'python -v' tells me it was built with gcc 3.4.4 (and has no trouble at
all finding site.py whether PYTHONHOME is defined or not). The
following code snippet:

comes back with '-Xlinker -export-dynamic'.

My own code needs to use Portland Group's pgi. I did some googling for
various permutations of nouns from the preceding few paragraphs and
found Pythonic mention of using "-Wl,-export-dynamic" as a flag for the
PG linker. OK, try that, builds fine, same error.

I cannot recompile Python on this machine and I don't really understand
exactly what is happening with the Py_* function calls in the C snippet
above, or whether I can get more detailed traceback info. This is the
first time I've tried embedding and it's rather obvious that I've run
into a problem that everyone but Messrs. van Rossum and Lundh has hit.
Somebody, somewhere must have an honest-to-glub solution. If you are
that somebody, please let me know what to do because I'm about to throw
in the towel and embed That Other Language.

Oh, one more thing: if I launch python from the shell and type in the
strings from the C snippet it works fine.

Thanks,


Jim

 

[Jim Hill]

Jim Hill (that'd be me) wrote:

I forgot one more key thing: the compiled code is being run via mpirun
(LAM/MPI). Might that have something to do with my pain and heartache?


Jim

(original post reproduced below in shocking breach of etiquette on the
off chance someone's interested in this post and didn't bother reading
the first.)

 

[Gabriel Genellina]

I want to do a simple embed, so I've followed the example in the
Extending and Embedding documentation:

In the .c file,

#include <Python.h>

int routine() {
Py_Initialize();
PyRun_SimpleString("from time import time,ctime\n"
"print 'Today is',ctime(time())\n");
Py_Finalize();
return 0;
}

(Why routine() and not main()? Unfortunately you can't repeteadly
initialize/finalize the interpreter, you must do that only once.)

The code compiles just fine, but when I execute it the call to
Py_Initialize() comes back with:

'import site' failed; use -v for traceback
Traceback (most recent call last):
File "<string>", line 1, in <module>
ImportError: No module named time

Try this:
PyRun_SimpleString("import sys; print sys.path");
to see where Python expects to find its library (or call the Py_GetPath
function).

You may need to call Py_SetProgramName (before Py_Initialize) so it can
find where the standard library resides.
At least for testing purposes, you can copy your executable into the same
directory where Python is installed.

 

[Jim Hill]

(Why routine() and not main()? Unfortunately you can't repeteadly
initialize/finalize the interpreter, you must do that only once.)

This is a small routine tucked off to the side of a fairly large
mostly-FORTRAN-with-some-C program. I need to parse a slash-delimited
input file from a different program and fill up some arrays with the
results. Rather than wrestle with FORTRAN's wretched file I/O I thought
I'd do it this way.

Try this:
PyRun_SimpleString("import sys; print sys.path");
to see where Python expects to find its library (or call the Py_GetPath
function).

It returned a list of paths nearly identical to what the interactive
interpreter does -- it's on a different machine and too long to retype
here -- the interactive sys.path has an empty string as item 0, while
the embedded sys.path returns the interactive[1:n].

You may need to call Py_SetProgramName (before Py_Initialize) so it can
find where the standard library resides.

Didn't do anything, alas.

At least for testing purposes, you can copy your executable into the same
directory where Python is installed.

No can do -- it's not my machine and I don't have appropriate
privileges. Thanks for trying to help me out but I'm on a crash
deadline and it looks like I'll be doing some C parsing. Blech.


Jim