def _add_vessel_class(df):
    "Creates 'Class' column based on vessel LOA ft."
    df.loc[:, 'Class'] = 'Panamax'
    post_row = (df.loc[:, 'LOA ft'] > 965)
    post_loc = df.loc[post_row, :].index
    post_pan = df.index.isin(post_loc)
    df.loc[(post_pan, 'Class')] = 'Post-Panamax'
    return df
Creates 'Class' column based on vessel LOA ft.
def _add_vessel_class(df):
    
    df.loc[:, 'Class'] = 'Panamax'
    post_row = (df.loc[:, 'LOA ft'] > 965)
    post_loc = df.loc[post_row, :].index
    post_pan = df.index.isin(post_loc)
    df.loc[(post_pan, 'Class')] = 'Post-Panamax'
    return df