def remove_nan_entries(df, key_columns, verbose=True):
    n_row = len(df)
    for column in key_columns:
        df = df[(df[column] == df[column])]
    if verbose:
        print('Prune ({}/{}) rows.'.format((n_row - len(df)), n_row))
    return df
def remove_nan_entries(df, key_columns, verbose=True):
    n_row = len(df)
    for column in key_columns:
        df = df[(df[column] == df[column])]
    if verbose:
        print('Prune ({}/{}) rows.'.format((n_row - len(df)), n_row))
    return df