def data_format(df):
    """
    Convert each column to the correct format.
    :param df: the dataframe
    :return: the dataframe
    """
    for key in df.columns:
        if key == 'Postal code' or key == 'Area':
            df[key] = df[key].astype('object')
        else:
            df[key] = df[key].astype('float')
    return df