Dropping rows from a df rises a SettingWithCopyWarning error (Pandas, Python) when value doesn't exist (using inplace=T)?

Question

I am trying to drop some rows based on a specific value of a dataframe:

dd = {'ae': pd.DataFrame(dict(a=[1,2,4], b=[4,5,6])),
      'be': pd.DataFrame(dict(a=[13,21,413], b=[456,54,62]))}
def test_remove(dd, val):
      test = dd.get('ae')
      test.drop(test.loc[test['a']==val].index, inplace=True)
test_remove(dd, 24242)

But I am getting the following error:

/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pandas/core/frame.py:4906: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame

Please advise what is wrong here? I have a dictionary of dataframes, I am trying to get into each of them and remove a row based on a specific column value.

Answer 1

Rather than doing the remove in place, it would be better to do something like this:

dd = {'ae': pd.DataFrame(dict(a=[1,2,4], b=[4,5,6])),
      'be': pd.DataFrame(dict(a=[13,21,413], b=[456,54,62]))}
def remove_rows(dd, key, val, col):
    dd[key] = dd[key].drop(dd[key].loc[dd[key][col]==val].index)
    return dd
dd = remove_rows(dd, 'ae', 413, 'a')