def categorical(df):
    """ Extract names of categorical column
    
    This function accepts a dataframe and returns categorical list,
    containing the names of categorical columns(categorical_var).
    
    Keyword arguments:
    df - Pandas dataframe from which the columns name will be extracted
        
    Returns:
    categorical_var - List of categorical features
    """
    categorical_var = df.select_dtypes(include = 'object')
    return categorical_var.columns