combinations.py

def combinations(input_string):
    d = {'2': 'abc',
         '3': 'def',
         '4': 'ghi',
         '5': 'jkl',
         '6': 'mno',
         '7': 'pqrs',
         '8': 'tuv',
         '9': 'wxyz'}

    if input_string == '':
        return ['']

    data = []
    word = d[input_string[-1]]

    for combination in combinations(input_string[:-1:]):
        for c in word:
            data.append(combination + c)

    return data


print(' '.join(combinations(input())))