data = {'a': [np.nan, 0, 0, 0, 0, 0, np.nan, 0, 0, 0, 0, 0, 9, 9], 'b': [np
    .nan, np.nan, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 7], 'c': [np.nan, np.nan,
    1, 1, 2, 2, 3, 3, 3, 1, 1, 1, 1, 1], 'd': [np.nan, np.nan, 7, 9, 6, 9, 
    7, np.nan, 6, 6, 7, 6, 9, 6]}
df = pd.DataFrame(data, columns=['a', 'b', 'c', 'd'])
Select rows where at least one value from the list of columns is not null