def cols_to_rename(df, dictionary):
    """Drop selected columns and return dataframe.
    
    Args: 
        df: Pandas dataframe.
        dictionary: {'old_name1': 'new_name1', 'old_name2': 'new_name2'}

    Returns: 
        Original dataframe without dropped columns.
    """
    df.rename(dictionary, axis=1, inplace=True)
    return df
