def prune_table(df):
    """
    Removes columns where all values are duplicates
    """
    dupl_names = []
    for column_name in df.columns:
        if len(set(df[column_name])) == 1:
            dupl_names.append(column_name)

    if dupl_names and len(df) > 1:
        df = df.drop(dupl_names, axis=1)
    return df