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({})
        new_response['users'][-1]['id'] = user.get('id')
        new_response['users'][-1]['surname'] = user.get('surname')
        new_response['users'][-1]['avatar_id'] = user.get('avatar_id')
        new_response['users'][-1]['specialty_ids'] = []
        for specialty in user.get('specialty_ids'):
            new_response['users'][-1]['specialty_ids'].append({})
            new_response['users'][-1]['specialty_ids'][-1]['id'] = specialties[specialty]['id']
            new_response['users'][-1]['specialty_ids'][-1]['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))