Get next and previous item in dictionary using Python

Question

I have an dictionary as follows:

defaultdict(None, {
    'Category 1': [
        {'id': 24, 'name': 'Video 1', 'cat_id': 16, 'tut_id': 14, 'description': ''}, 
        {'id': 28, 'name': 'Video 5', 'cat_id': 16, 'tut_id': 14, 'description': ''}
    ], 
    'Category 3': [
        {'id': 25, 'name': 'Video 3', 'cat_id': 18, 'tut_id': 14, 'description': ''}, 
        {'id': 29, 'name': 'Video 6', 'cat_id': 18, 'tut_id': 14, 'description': ''}
    ], 
    'Category 2': [
        {'id': 26, 'name': 'Video 2', 'cat_id': 17, 'tut_id': 14, 'description': ''}, 
        {'id': 27, 'name': 'Video 4', 'cat_id': 17, 'tut_id': 14, 'description': ''}
    ]
})

And in my view I have next code:

video_id = int(request.POST.get('id', None))
cat_id = int(request.POST.get('cat_id', None))
cat_name = int(request.POST.get('cat_name', None))
tut_id = int(request.POST.get('tut_id', None))

I want to get next and previous item from the dictionary. If there are items onder same category get them, and if there are not, get the item from the next or previous category.

I have no idea how to start

Expected output

video_id = 3
cat_id = 18
cat_name = "Category 3"
tut_id = 14

next = {'id': 29, 'name': 'Video 6', 'cat_id': 18, 'tut_id': 14, 'description': ''}
prev = {'id': 28, 'name': 'Video 5', 'cat_id': 16, 'tut_id': 14, 'description': ''}

Any idea how to do that?

[Have a look at it](https://stackoverflow.com/questions/28035490/in-python-how-can-i-get-the-next-and-previous-keyvalue-of-a-particular-key-in/28035679) — Abhi, Oct 07 '19 at 06:03
Possible duplicate of [In Python, How can I get the next and previous key:value of a particular key in a dictionary?](https://stackoverflow.com/questions/28035490/in-python-how-can-i-get-the-next-and-previous-keyvalue-of-a-particular-key-in) — Ana, Oct 07 '19 at 06:10
Are you allowed to store the data in a different structure for easier access? Or does the data specifically have to be stored in this structure? — Diptangsu Goswami, Oct 07 '19 at 06:51

Diptangsu Goswami · Answer 1 · 2019-10-07T09:45:23.213

The defaultdict can be flattened to a list of dicts like this. Assuming, you're using the latest version of python, a dict object maintains the order in which elements were inserted.

from pprint import pprint

d = defaultdict(None, {
    'Category 1': [
        {'id': 24, 'name': 'Video 1', 'cat_id': 16, 'tut_id': 14, 'description': ''}, 
        {'id': 28, 'name': 'Video 5', 'cat_id': 16, 'tut_id': 14, 'description': ''}
    ], 
    'Category 3': [
        {'id': 25, 'name': 'Video 3', 'cat_id': 18, 'tut_id': 14, 'description': ''}, 
        {'id': 29, 'name': 'Video 6', 'cat_id': 18, 'tut_id': 14, 'description': ''}
    ], 
    'Category 2': [
        {'id': 26, 'name': 'Video 2', 'cat_id': 17, 'tut_id': 14, 'description': ''}, 
        {'id': 27, 'name': 'Video 4', 'cat_id': 17, 'tut_id': 14, 'description': ''}
    ]
})

dicts = []
for v in d.values():
    dicts.extend(v)

pprint(dicts)

Output:

[{'cat_id': 16, 'description': '', 'id': 24, 'name': 'Video 1', 'tut_id': 14},
 {'cat_id': 16, 'description': '', 'id': 28, 'name': 'Video 5', 'tut_id': 14},
 {'cat_id': 18, 'description': '', 'id': 25, 'name': 'Video 3', 'tut_id': 14},
 {'cat_id': 18, 'description': '', 'id': 29, 'name': 'Video 6', 'tut_id': 14},
 {'cat_id': 17, 'description': '', 'id': 26, 'name': 'Video 2', 'tut_id': 14},
 {'cat_id': 17, 'description': '', 'id': 27, 'name': 'Video 4', 'tut_id': 14}]

From what I inferred, the category name is not required in the output.
After reshaping the data in this format, the required data can be extracted using a for loop.

video_id = 3
cat_id = 18
cat_name = "Category 3"
tut_id = 14


idx = -1
found = False
while(idx < len(dicts)):
    idx += 1
    video_id_i = int(dicts[idx]['name'].split()[1])
    if video_id == video_id_i:
        found = True
        break

# TODO: check for index out of bounds
if found:
    prev = dicts[idx - 1]
    curr = dicts[idx]
    next = dicts[idx + 1]

    print(prev, curr, next, sep='\n')

Output:

{'id': 28, 'name': 'Video 5', 'cat_id': 16, 'tut_id': 14, 'description': ''}
{'id': 25, 'name': 'Video 3', 'cat_id': 18, 'tut_id': 14, 'description': ''}
{'id': 29, 'name': 'Video 6', 'cat_id': 18, 'tut_id': 14, 'description': ''}

Get next and previous item in dictionary using Python

1 Answers1