NameError during MDF v4 file load: name 'x' is not defined

[JohnLamerton]

Python version

3.11.9 (tags/v3.11.9:de54cf5, Apr 2 2024, 10:12:12) [MSC v.1938 64 bit (AMD64)]

Platform information

Windows-10-10.0.19045-SP0

Numpy version

1.25.0

mdfreader version

4.1

Description

The following error occurs when loading a specific MDF v4 file using the Mdf class:
NameError: name 'x' is not defined

It appears to me that the issue may lie within a maths channel that's present in the source mdf file?

The MDF ID info from a relevant file is:
id_file = b'MDF '
id_vers = b'4.10 '
id_prog = b'MCD17.07'
id_ver = 410
id_unfi_flags = 0
id_custom_unfi_flags = 0

The relevant portion of the call stack is shown below:
"\file\vehicle_file.py", line 585, in read_mdf
file_data = Mdf(file_name)
^^^^^^^^^^^^^^
File ".venv\Lib\site-packages\mdfreader\mdf.py", line 150, in init
self.read(file_name, channel_list=channel_list,
File ".venv\Lib\site-packages\mdfreader\mdfreader.py", line 419, in read
self.read4(self.fileName, None, multi_processed, channel_list,
File ".venv\Lib\site-packages\mdfreader\mdf4reader.py", line 1538, in read4
self._convert_all_channel4()
File ".venv\Lib\site-packages\mdfreader\mdf4reader.py", line 1661, in _convert_all_channel4
[self._convert_channel4(channelName) for channelName in self]
File ".venv\Lib\site-packages\mdfreader\mdf4reader.py", line 1661, in
[self._convert_channel4(channelName) for channelName in self]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".venv\Lib\site-packages\mdfreader\mdf4reader.py", line 1649, in _convert_channel4
self.set_channel_data(channel_name, self._get_channel_data4(channel_name))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".venv\Lib\site-packages\mdfreader\mdf4reader.py", line 1567, in _get_channel_data4
return self._convert_channel_data4(self.get_channel(channel_name), channel_name,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".venv\Lib\site-packages\mdfreader\mdf4reader.py", line 1613, in _convert_channel_data4
vector = _formula_conversion(vector, conversion_parameter['cc_ref']['Comment'])
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".venv\Lib\site-packages\mdfreader\mdf4reader.py", line 2343, in _formula_conversion
return expr(vector)
^^^^^^^^^^^^
File "", line 2, in _lambdifygenerated
return 100*5/x
^

[ratal]

Hi,
The ASAM mdf specification do not mention what shall be the name of the variable. mdfreader is expecting 'X' generally used but it is possible that your mdf logger uses another variable name, here 'x', lower case.
You can try to adjust code for your use case or create variable name change based on exception. Unfortunately there is not universal solution than this custom approach for this.

[JohnLamerton]

Thanks for your swift response @ratal, I will investigate the solutions that you've suggested.

[JohnLamerton]

After performing some investigation I have found that the simple change highlighted in the image below resolves the issue for me (changing the "formula" variable to upper case). Of course, this solution only works robustly if we can guarantee that the "formula" input argument is always of type string. I know that you mention that this doesn't align with the ASAM specification, but if this solution is robust then it might be useful for other users. Do you think this solution is suitable for inclusion in the mdfreader package @ratal ?

[ratal]

Ok seems good idea to force the formula being upper case, as expected variable is 'X' in upper case. You can propose for a pull request and I can do some tests to confirm eventual regressions.

[JohnLamerton]

Thanks for the feedback @ratal, I've created a pull request here: #219

We can continue the conversation there so I'll close this Issue :)