def normalize_columns(df, colnames):
    """Normalizes the specified columns in dataframe using min-max normalization
    :param df: df being normalized
    :param colnames: list of columns to be normalized
    :return: df with normalized columns
    """
    for col in colnames:
        s = df[col]
        df[col] = s.sub(s.min()).div((s.max() - s.min()))
    print(f'''Normalized Columns: {colnames}''')

    return df