以更优雅的方式打印循环字典

Question

I am reading "Data Science from Scratch" by Jeol Grus, which is more than 20 years later since my university course of Data Structure. Fascinated by the elegant way he writes the code. In the example of chapter 1, I am interested in the data structure of appending own dictionary to itself - 'users'. When I try to understand how it works within the dictionary by printing the contents of 'users', it prints out infinite loops of that dictionary. And more amazing, no error from Python. But I still have no idea what the contents are.

Searched over some articles, found one on Quora How do I nicely print a nested dictionary in Python? , and understood the contents. Though I start thinking if I can print out the contents in more concise style, like below, with pointers to the dictionary, or similar, instead of repetitive loops. Possible?

{"id": 0, "name": "Hero", "friend": [*users[1], *users[2]] }
{"id": 1, "name": "Dunn", "friend": [*users[2], *users[3]] }

Example from Data Science from Scratch

users = [
        { "id": 0, "name": "Hero"},
        { "id": 1, "name": "Dunn"},
        { "id": 2, "name": "Sue"},
        { "id": 3, "name": "Chi"},
        { "id": 4, "name": "Thor"},
        { "id": 5, "name": "Clive"},
        { "id": 6, "name": "Hicks"},
        { "id": 7, "name": "Devin"},
        { "id": 8, "name": "Kate"},
        { "id": 9, "name": "Klein"}
]
friendship = [(0,1), (0,2), (1,2), (1,3), (2,3), (3,4),
              (4,5), (5,6), (5,7), (6,8), (7,8), (8,9)]

for user in users :
    user["friends"] = []

for i, j in friendship :
    users[i]["friends"].append(users[j])
    users[j]["friends"].append(users[i])

def number_of_friends(user) :
    """ how many friends does _user_ have """
    return(len(user["friends"]))

total_connection = sum(number_of_friends(user)
                       for user in users)
num_users = len(users)
avg_connection = total_connection / num_users

# create a list (user_id, number_of_friends)
num_friends_by_id = [(user['id'], number_of_friends(user))
                      for user in users]

Print out

{'id': 0, 'name': 'Hero', 'friends': [{'id': 1, 'name': 'Dunn', 'friends': [{...}, {'id': 2, 'name': 'Sue', 'friends': [{...}, {...}, {'id': 3, 'name': 'Chi', 'friends': [{...}, {...}, {'id': 4, 'name': 'Thor', 'friends': [{...}, {'id': 5, 'name': 'Clive', 'friends': [{...}, {'id': 6, 'name': 'Hicks', 'friends': [{...}, {'id': 8, 'name': 'Kate', 'friends': [{...}, {'id': 7, 'name': 'Devin', 'friends': [{...}, {...}]}, {'id': 9, 'name': 'Klein', 'friends': [{...}]}]}]}, {'id': 7, 'name': 'Devin', 'friends': [{...}, {'id': 8, 'name': 'Kate', 'friends': [{'id': 6, 'name': 'Hicks', 'friends': [{...}, {...}]}, {...}, {'id': 9, 'name': 'Klein', 'friends': [{...}]}]}]}]}]}]}]}, {'id': 3, 'name': 'Chi', 'friends': [{...}, {'id': 2, 'name': 'Sue', 'friends': [{...}, {...}, {...}]}, {'id': 4, 'name': 'Thor', 'friends': [{...}, {'id': 5, 'name': 'Clive', 'friends': [{...}, {'id': 6, 'name': 'Hicks', 'friends': [{...}, {'id': 8, 'name': 'Kate', 'friends': [{...}, {'id': 7, 'name': 'Devin', 'friends': [{...}, {...}]}, {'id': 9, 'name': 'Klein', 'friends': [{...}]}]}]}, {'id': 7, 'name': 'Devin', 'friends': [{...}, {'id': 8, 'name': 'Kate', 'friends': [{'id': 6, 'name': 'Hicks', 'friends': [{...}, {...}]}, {...}, {'id': 9, 'name': 'Klein', 'friends': [{...}]}]}]}]}]}]}]}, {'id': 2, 'name': 'Sue', 'friends': [{...}, {'id': 1, 'name': 'Dunn', 'friends': [{...}, {...}, {'id': 3, 'name': 'Chi', 'friends': [{...}, {...}, {'id': 4, 'name': 'Thor', 'friends': [{...}, {'id': 5, 'name': 'Clive', 'friends': [{...}, {'id': 6, 'name': 'Hicks', 'friends': [{...}, {'id': 8, 'name': 'Kate', 'friends': [{...}, {'id': 7, 'name': 'Devin', 'friends': [{...}, {...}]}, {'id': 9, 'name': 'Klein', 'friends': [{...}]}]}]}, {'id': 7, 'name': 'Devin', 'friends': [{...}, {'id': 8, 'name': 'Kate', 'friends': [{'id': 6, 'name': 'Hicks', 'friends': [{...}, {...}]}, {...}, {'id': 9, 'name': 'Klein', 'friends': [{...}]}]}]}]}]}]}]}, {'id': 3, 'name': 'Chi', 'friends': [{'id': 1, 'name': 'Dunn', 'friends': [{...}, {...}, {...}]}, {...}, {'id': 4, 'name': 'Thor', 'friends': [{...}, {'id': 5, 'name': 'Clive', 'friends': [{...}, {'id': 6, 'name': 'Hicks', 'friends': [{...}, {'id': 8, 'name': 'Kate', 'friends': [{...}, {'id': 7, 'name': 'Devin', 'friends': [{...}, {...}]}, {'id': 9, 'name': 'Klein', 'friends': [{...}]}]}]}, {'id': 7, 'name': 'Devin', 'friends': [{...}, {'id': 8, 'name': 'Kate', 'friends': [{'id': 6, 'name': 'Hicks', 'friends': [{...}, {...}]}, {...}, {'id': 9, 'name': 'Klein', 'friends': [{...}]}]}]}]}]}]}]}]}

Answer 1

Try using classes instead of dicts.

class Person:
    def __init__(self, id, name):
        self.id = id
        self.name = name
        self.friends = []

    def __str__(self):
        return "*users[" + str(id) + "]"