FAQ - Frequently Asked Questions#

New to pyXCP? See pyXCP Quickstart Guide for a 15-minute introduction.

Installation & Build Issues#

ModuleNotFoundError: No module named 'pyxcp.transport.transport_ext'#

This is a build issue where the C++ extensions weren’t compiled correctly. Try these solutions in order:

  1. Install from PyPI with pre-built wheels (recommended):

    pip install --upgrade pip
pip install pyxcp

  2. If that fails, install build dependencies first:

    Ubuntu/Debian:

    sudo apt update
sudo apt install build-essential cmake python3-dev libpython3-dev pybind11-dev
pip install pyxcp

    Windows:

    • Install Visual Studio Build Tools (workload “Desktop development with C++”)

      pip install pyxcp

    macOS:

    brew install cmake pybind11
pip install pyxcp

  3. Build from source manually:

    git clone https://github.com/christoph2/pyxcp.git
cd pyxcp
python build_ext.py
pip install -e .

Related issues: #240, #188, #199, #169

FileNotFoundError: 'cmake' on Ubuntu 24.04#

CMake is not installed. Install required build tools:

sudo apt update
sudo apt install build-essential cmake python3-dev libpython3-dev pybind11-dev
cmake --version
python3-config --libs

Then install pyxcp:

pip install pyxcp

Related issues: #169

UnboundLocalError: cannot access local variable 'libdir' during build#

The build system cannot find the Python development libraries. Install them:

sudo apt install python3-dev libpython3-dev
find /usr -name "libpython*.so"
find /usr -name "libpython*.a"

If the second command returns nothing, the Python link library is missing. Install the appropriate python3.X-dev package for your Python version.

Related issues: #169

PyInstaller/py2exe: pyxcp module not found after bundling#

PyInstaller needs to be told about the native extensions.

Option 1: hook file (recommended):

from PyInstaller.utils.hooks import collect_dynamic_libs

binaries = collect_dynamic_libs('pyxcp')
datas = [
    ('path/to/site-packages/pyxcp/*.pyd', 'pyxcp'),  # Windows
    ('path/to/site-packages/pyxcp/*.so', 'pyxcp'),   # Linux/macOS
]
hiddenimports = [
    'pyxcp.transport.transport_ext',
    'pyxcp.cpp_ext.cpp_ext',
    'pyxcp.daq_stim.stim',
    'pyxcp.recorder.rekorder',
]

Build:

pyinstaller --additional-hooks-dir=. your_script.py

Option 2: specify in .spec:

a = Analysis(
    ...
    hiddenimports=[
        'pyxcp.transport.transport_ext',
        'pyxcp.cpp_ext.cpp_ext',
        'pyxcp.daq_stim.stim',
        'pyxcp.recorder.rekorder',
    ],
    ...
)

Related issues: #261, #203

Configuration#

getDaqInfo() fails or returns empty event channels#

As of v0.26.x, getDaqInfo() treats optional DAQ services (e.g., GET_DAQ_PROCESSOR_INFO, GET_DAQ_RESOLUTION_INFO, GET_DAQ_EVENT_INFO) defensively (Issue #253). The returned dict now includes valid flags for processor, resolution, and events to indicate whether data came from the slave or safe defaults. If processor/resolution are False, supply trusted values via DaqProcessor.setup(daq_info_override=...) or abort—relying on defaults can lead to incomplete DAQ setup. If events is False, the event list will be empty; you can still run DAQ if your configuration uses predefined events.

Related issues: #253

DaqToCsv fails with FileNotFoundError when running from Robot Framework#

Fixed in v0.26.4+. DaqToCsv and other DAQ classes now work without requiring a configuration file.

Common causes:

  • Different working directory in test runners

  • Missing logger/config

Solutions:

  1. Pass a logger explicitly (recommended):

    import logging
from pyxcp.daq_stim import DaqToCsv

logger = logging.getLogger("my_daq_logger")
logger.addHandler(logging.StreamHandler())
logger.setLevel(logging.INFO)
daq_policy = DaqToCsv(daq_lists, logger=logger)

  2. Robot Framework:

    *** Settings ***
Library  pyxcp.daq_stim

*** Test Cases ***
My DAQ Test
    ${logger} =  Get Logger  my_robot_logger
    ${daq_policy} =  Create DaqToCsv  ${daq_lists}  logger=${logger}

  3. Set PYXCP_CONFIG (v0.26.5+):

    export PYXCP_CONFIG=/absolute/path/to/pyxcp_conf.py

  4. Programmatic configuration (v0.26.5+):

    from pyxcp.config import create_application_from_config

config = {"Transport": {"CAN": {"device": "socketcan", "channel": "can0", "bitrate": 500000}}}
app = create_application_from_config(config)

Config file search order (v0.26.5+):

  1. PYXCP_CONFIG env var (absolute path)

  2. Current working directory

  3. Script directory

  4. User home ~/.pyxcp/pyxcp_conf.py

Related issues: #260