# Erlang-\>C++-\>Python-\>C/C++ Import Error: undefined symbol: PyObject\_SelfIter **URL:** \ **Category:** Questions / Help\ **Tags:** port\_driver, erlang-otp\ **Created:** [October 18, 2022, 10:40pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959 "2022-10-18T22:40:05Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Sparky](https://erlangforums.com/user_avatar/erlangforums.com/sparky/32/1685_2.png) [@Sparky](https://erlangforums.com/u/Sparky)\ **Post date:** [October 18, 2022, 10:40pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/1 "2022-10-18T22:40:05Z")
I’m trying to run a Python function from Erlang using a C++ driver. I am able to run the Python function outside of Erlang by calling the C++ driver function and everything works perfectly, but when I try to call it from Erlang, I get the following import error: ```erlang ImportError: /######/lib/python3.8/site-packages/grpc/_cython/cygrpc.cpython-38-x86_64-linux-gnu.so: undefined symbol: PyObject_SelfIter ``` This error happens when the C++ driver runs the PyImport\_Import() function on the Python file. It looks like the shared library mentioned in the error is trying to access the “Python.h” file and can’t find it. I tried adding its location to the PATH environment variable (using Py\_SetPath()) but that did not solve the issue. My C++ driver uses the “Python.h” file, but I have to include the path at compile time or else I get a similar import error. Is there a specific environment variable I need to set in my rebar3.config file or elsewhere to allow the mentioned shared library to find the “Python.h” file? Or is there something else I’m doing (or not doing) that is causing this error? ---
**Author:** ![starbelly](https://erlangforums.com/user_avatar/erlangforums.com/starbelly/32/209_2.png) [@starbelly](https://erlangforums.com/u/starbelly)\ **Post date:** [October 18, 2022, 10:41pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/2 "2022-10-18T22:41:08Z")
It sounds like your `LD_LIBRARY_PATH` simply doesn’t have ` /######/lib/python3.8/site-packages/grpc/_cython/` on it. Make sure this is set before launching from erlang. ---
**Author:** ![Sparky](https://erlangforums.com/user_avatar/erlangforums.com/sparky/32/1685_2.png) [@Sparky](https://erlangforums.com/u/Sparky)\ **Post date:** [October 18, 2022, 10:53pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/3 "2022-10-18T22:53:49Z")
@starbelly, thanks for responding. I did try setting that variable in my C++ driver (using setenv) before running Py\_Initialize(), but that didn’t fix the issue. Do I need to set it in a different place? ---
**Author:** ![starbelly](https://erlangforums.com/user_avatar/erlangforums.com/starbelly/32/209_2.png) [@starbelly](https://erlangforums.com/u/starbelly)\ **Post date:** [October 18, 2022, 11:11pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/4 "2022-10-18T23:11:14Z")
You need to set in your shell before you boot erlang, that’s how I’ve always handled these issues. ---
**Author:** ![Sparky](https://erlangforums.com/user_avatar/erlangforums.com/sparky/32/1685_2.png) [@Sparky](https://erlangforums.com/u/Sparky)\ **Post date:** [October 18, 2022, 11:20pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/5 "2022-10-18T23:20:33Z")
Ok, I tried running `export LD_LIBRARY_PATH=/######/lib/python3.8/site-packages/grpc/_cython/` before running `rebar3 shell`, but I’m still getting the error. I also tried doing the same thing but setting `LD_LIBRARY_PATH` to the location of `Python.h` but that didn’t work either. ---
**Author:** ![starbelly](https://erlangforums.com/user_avatar/erlangforums.com/starbelly/32/209_2.png) [@starbelly](https://erlangforums.com/u/starbelly)\ **Post date:** [October 18, 2022, 11:25pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/6 "2022-10-18T23:25:17Z")
QQ: I’m assuming you didn’t literally use `/######/...` instead you used `######` in this thread to obfuscate a path on your system. Is that correct? ---
**Author:** ![Sparky](https://erlangforums.com/user_avatar/erlangforums.com/sparky/32/1685_2.png) [@Sparky](https://erlangforums.com/u/Sparky)\ **Post date:** [October 18, 2022, 11:26pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/7 "2022-10-18T23:26:43Z")
That is correct. Speaking of which, is there a better way to indicate this? ---
**Author:** ![starbelly](https://erlangforums.com/user_avatar/erlangforums.com/starbelly/32/209_2.png) [@starbelly](https://erlangforums.com/u/starbelly)\ **Post date:** [October 18, 2022, 11:34pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/8 "2022-10-18T23:34:23Z")
Not really 🙂 Maybe say so next time to be clear. It sounds like you’re still missing some libs on your LD\_LIBRARY\_PATH. Now that I look back at the error, you’re missing part of python itself on your LD\_LIBRARY\_PATH. This could also be due to linking problems. I’d do some googling on the error 🙂 ---
**Author:** ![Sparky](https://erlangforums.com/user_avatar/erlangforums.com/sparky/32/1685_2.png) [@Sparky](https://erlangforums.com/u/Sparky)\ **Post date:** [October 19, 2022, 3:09pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/9 "2022-10-19T15:09:46Z")
I have spent about a week googling the error and trying various things with no success. What makes me think it is Erlang related is the fact that the code runs fine outside of Erlang (calling the driver functions directly from C++). It’s when I try to run it from inside Erlang that I get the error. ---
**Author:** ![filmor](https://erlangforums.com/user_avatar/erlangforums.com/filmor/32/988_2.png) [@filmor](https://erlangforums.com/u/filmor)\ **Post date:** [October 23, 2022, 8:16pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/10 "2022-10-23T20:16:25Z")
The error indicates that `libpython` is not loaded. How do you usually run this code? What does `ldd your_driver.so` show? ---
**Author:** ![Sparky](https://erlangforums.com/user_avatar/erlangforums.com/sparky/32/1685_2.png) [@Sparky](https://erlangforums.com/u/Sparky)\ **Post date:** [October 26, 2022, 3:08pm UTC](https://erlangforums.com/t/erlang-c-python-c-c-import-error-undefined-symbol-pyobject-selfiter/1959/11 "2022-10-26T15:08:36Z")
Here’s the output of ldd: ```erlang linux-vdso.so.1 (0x00007ffe9b5cc000) libpython3.8.so.1.0 => /lib/x86_64-linux-gnu/libpython3.8.so.1.0 (0x00007f8196ccd000) libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f8196adb000) libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007f8196aad000) libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f8196a91000) libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f8196a6e000) libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f8196a68000) libutil.so.1 => /lib/x86_64-linux-gnu/libutil.so.1 (0x00007f8196a61000) libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f8196912000) /lib64/ld-linux-x86-64.so.2 (0x00007f8197248000) ``` What’s weird is the fact that my C++ driver uses libpython to setup and start the Python interpreter, so it has to be loaded. But it seems as though inside the Python interpreter, it can’t access it. In normal operation (from Erlang), I load the driver, start the driver, and then do a port\_control call to execute Python call, although I haven’t gotten past starting the driver, since that’s where I run into the issue. The C++ driver just returns 0 for the init call. In the start call, it does a Py\_SetPath, Py\_Initialize, and then attempts the PyImport\_Import at which point it runs into the import error. I have tried adding the path to libpython in the Py\_SetPath command as well, with no luck. And just to reiterate, when I run the C++ driver outside of Erlang, all is well. But when I try to run it from Erlang, I get this issue.