naked_twins.py

def naked_twins(values):
    """Eliminate values using the naked twins strategy.
    Args:
        values(dict): a dictionary of the form {'box_name': '123456789', ...}

    Returns:
        the values dictionary with the naked twins eliminated from peers.
    """
    
    twins = []
    
    # Find all instances of naked twins
    for box in values.keys():
        for unit_list in units[box]:
            for unit in unit_list:
                if values[unit] == values[box]:
                    twins.append([box, unit_list])

    # Eliminate the naked twins as possibilities for their peers
    for box, unit_list in twins:
        for unit in unit_list:
            for value in values[box]:
                if value in values[unit] and len(values[unit]) > 1 and values[unit] != values[box]:
                    values[unit] = values[unit].replace(value,'')

    return values