[bug] reference_column assigned incorrectly on creation of groups

awarsewa commented 4 months ago

Bug report checklis

[X] Searched the issues page for similar reports
[X] Read the relevant sections of the documentation
[X] Browse the tutorials and tests for usefull code snippets and examples of use
[X] Reproduced the issue after updating with pip install --upgrade pandapower (or git pull)
[X] Tried basic troubleshooting (if a bug/error) like restarting the interpreter and checking the pythonpath

Reproducible Example

import pandapower as pp

net = pp.networks.example_simple()
pp.create_group(net, ['switch', 'line'], [[0, 1], [0, 1]])
pp.attach_to_group(net, 0, ['switch'], [[2]])
print(net.switch)

Issue Description and Traceback

When you create a group, the "reference_column" of the newly created group is set to NaN. On adding an element, comparison of NaN to None in attach_to_group yields different reference columns. This leads to a "nan"-column being added to net.switch in groups.py line 975:

net[et][reference_column].loc[idxs] = ["%s_%i_%s" % (et, idx, str(
                    uuid.uuid4())) for idx in idxs]

Expected Behavior

Check for different reference columns in attach_to_group should either handle NaN or entries in reference_column of a newly created group should be set to None instead.

Installed Versions

INSTALLED VERSIONS

commit : d9cdd2ee5a58015ef6f4d15c7226110c9aab8140 python : 3.12.4.final.0 python-bits : 64 OS : Windows OS-release : 10 Version : 10.0.19045 machine : AMD64 processor : Intel64 Family 6 Model 140 Stepping 1, GenuineIntel byteorder : little LC_ALL : None LANG : en LOCALE : de_DE.cp1252

pandas : 2.2.2 numpy : 1.26.4 pytz : 2024.1 dateutil : 2.9.0.post0 setuptools : 69.5.1 pip : 24.0 Cython : None pytest : None hypothesis : None sphinx : None blosc : None feather : None xlsxwriter : None lxml.etree : None html5lib : None pymysql : None psycopg2 : None jinja2 : None IPython : 8.26.0 pandas_datareader : None adbc-driver-postgresql: None adbc-driver-sqlite : None bs4 : None bottleneck : None dataframe-api-compat : None fastparquet : None fsspec : None gcsfs : None matplotlib : 3.9.0 numba : 0.60.0 numexpr : None odfpy : None openpyxl : 3.1.5 pandas_gbq : None pyarrow : None pyreadstat : None python-calamine : None pyxlsb : None s3fs : None scipy : 1.13.1 sqlalchemy : None tables : None tabulate : None xarray : None xlrd : None zstandard : None tzdata : 2024.1 qtpy : None pyqt5 : None

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vogt31337 commented 1 week ago

@awarsewa I do not really understand your problem. I think you have to create a group first. But I will do maintenance on the grouping features in pandapower shortly.

awarsewa commented 1 week ago

Thanks for looking into it. As you can see in the example code above, I have created a group in the first step and then tried adding an element to it. This is when I experienced some odd behaviour with a NaN column being added to the net.switch table. I might have misunderstood how you're supposed to use the grouping feature, but it looks like a bug to me.

e2nIEE / pandapower