How to modify the last node of a nested dictionary?

Question

Consider that you have a nested dictionary as the following:

{
    "text": "hi",
    "next": {
        "text": "hi",
        "next": {
            "text": "hi",
        }
    }
}

Now I want to change the last node to {"text": "bye"}, so that my end result is as follows:

{
    "text": "hi",
    "next": {
        "text": "hi",
        "next": {
            "text": "bye",
        }
    }
}

Remember that there can be thousands of nodes but I want to modify just the last node. How can I do it?

Thousands ? You will have [problems](https://stackoverflow.com/questions/3323001/what-is-the-maximum-recursion-depth-in-python-and-how-to-increase-it) then. — keepAlive, Aug 22 '21 at 15:00
I am not writing it in python but i want the solution in python so that i can understand the concept — Saptak Bhoumik, Aug 22 '21 at 15:02

eroot163pi · Accepted Answer · 2021-08-22T15:16:50.307

1

Looping through dictionary, getting last object and changing it

d = {
"text":"hi",
"next":{
        "text":"hi",
        "next":{
                "text":"bye"
                  }
}
}

pre = d
while True:
    next_ = pre.get('next')
    if not next_:
        pre['text'] = 'bye'
        break
    pre = next_
print(d)

edited Aug 22 '21 at 15:16

answered Aug 22 '21 at 15:09

eroot163pi

1,791
1
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This is not a recursive solution. – keepAlive Aug 22 '21 at 15:10
@keepAlive So what? – Kelly Bundy Aug 22 '21 at 15:10
What is the title of the question @Kelly ? Ah no... ***You are right***... I read too fast. – keepAlive Aug 22 '21 at 15:10
Dictionary is recursive, they dont require recursion, – eroot163pi Aug 22 '21 at 15:10
1

@keepAlive That they have a recursive *dictionary* structure. Not that they want a recursive solution. – Kelly Bundy Aug 22 '21 at 15:11
I need to access 'next' value in pre, so i use get, since it also checks if exist by returning vALUE OR NONE – eroot163pi Aug 22 '21 at 15:12

score 1 · Answer 2 · answered Aug 22 '21 at 15:11

1

if you know the depth of the dictionary, you can use reduce as explained here:

from functools import reduce
def reduce_dict(data, items):
    return reduce(dict.get, items, data)
depth = 1000
reduce_dict(my_dict, ['next']* depth)['text'] = 'bye'

answered Aug 22 '21 at 15:11

Mohammad

3,276
2
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If we have the depth, we might also have the tail and just do `tail['text'] = 'bye'` :-) – Kelly Bundy Aug 22 '21 at 15:23
Depending on how you are collecting the information, it is not uncommon to be provided with the constraints of the input (here the depth) to properly process the data. Having `tail`, while convenient is not that common. – Mohammad Aug 22 '21 at 15:27

score 1 · Answer 3 · answered Aug 22 '21 at 15:14

1

root = {'text': 'hi', 'next': {'text': 'hi', 'next': {'text': 'hi'}}}

node = root
while 'next' in node:
    node = node['next']
node['text'] = 'bye'

print(root)

Output:

{'text': 'hi', 'next': {'text': 'hi', 'next': {'text': 'bye'}}}

answered Aug 22 '21 at 15:14

Kelly Bundy

23,480
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How to modify the last node of a nested dictionary?

3 Answers3