def beautify_response(response):
    new_response = {'users': []}

    specialties = {}
    for specialty in response['specialties']:
        specialties[specialty['id']] = {'id': specialty['id'], 'title':specialty['title']}

    for user in response['users']:
        new_response['users'].append({})
        last_user = new_response['users'][-1]

        last_user['id'] = user.get('id')
        last_user['surname'] = user.get('surname')
        last_user['avatar_id'] = user.get('avatar_id')
        last_user['specialities'] = []

        for specialty in user.get('specialty_ids'):
            last_user['specialities'].append({})
            last_speciality = last_user['specialities'][-1]
            last_speciality['id'] = specialties[specialty]['id']
            last_speciality['title'] = specialties[specialty]['title']
    return new_response


response = {
    'users': [
        {
            'id': 129,
            'surname': 'Петров',
            'specialty_ids': [
                63
            ],
            'avatar_id': None
        }
    ],
    'specialties': [
        {
            'id': 63,
            'title': 'Программист'
        }
    ]
}

print(beautify_response(response))