Populate Python dictionaries with pre-assigned keys and values of a particular length

Question

Say for example I have the following dictionary in Python:

memory_map = {'data': [1,2,3], 'theta': [4,5,6,7]}

I would like to create another random dictionary that is identical to memory_map, has the same keys and the same lengths of lists as their values however the elements of the list are populated with random values using the np.random.default_rng(seed).uniform(low, high, size) function.

An example would be: random_dict = {'data': [5,3,1], 'theta': [7,3,4,8]}.

Moreover, if the names of the keys or the lengths of the lists in values change, this should automatically be reflected in the random_dict that is created.

If I add a new key or remove a key from the memory_map this should also be reflected in the random_dict.

So far, I have random_dict = {item: [] for item in list(memory_map.keys())} but am unsure of how to populate the empty list with the random values of the same length.

Thanks.

`import random`; `random_dict = {k: [random.randint(1, 9) for _ in v] for k, v in memory_map.items()}` — Samwise, Oct 04 '21 at 16:17
So if you add a new key to memory map it should add a new key to random_dict? — Dani Mesejo, Oct 04 '21 at 16:18
Can you post what have you tried so far. Looks like a fairly simple problem and can be solved with loop. — Abhishek, Oct 04 '21 at 16:18
I have added some more info to the question and also what I have tried so far. Thanks. — Zohim Chandani, Oct 04 '21 at 16:29

score 0 · Answer 1 · answered Oct 04 '21 at 16:24

Looks like you want something like this.

import random
import itertools


def shuffle_map(input_map):
    # Grab a list of all values
    all_values = list(itertools.chain(*input_map.values()))
    random.shuffle(all_values)  # Shuffle it

    new_map = {}  # Initialize a new map
    i = 0  # Keep track of how many items we've consumed
    for key, value in input_map.items():
        n = len(value)  # How many values per this key
        new_map[key] = all_values[i : i + n]  # Assign a slice
        i += n

    return new_map


memory_map = {"data": [1, 2, 3], "theta": [4, 5, 6, 7]}
print(shuffle_map(memory_map))

This prints out (e.g., consecutive runs)

{'data': [1, 5, 7], 'theta': [2, 4, 3, 6]}
{'data': [6, 7, 1], 'theta': [5, 4, 3, 2]}
{'data': [5, 2, 3], 'theta': [7, 6, 4, 1]}

Thanks for your suggestion. What if I wanted to populate the lists using `np.random.default_rng(seed).uniform(low, high, size)`? — Zohim Chandani, Oct 04 '21 at 16:37

score 0 · Answer 2 · answered Oct 04 '21 at 16:24

0

For the random lists you should take a look at the random module in the standard library, specifically at the random.sample or random.choices, depending on your needs. For the second request, of automatically update the dictionary based on changes of the first, the easiest way to do it is to create a wrapper around the first dict inheriting from the collections.UserDict class

answered Oct 04 '21 at 16:24

ale-cci

153
2
11

You don't need to inherit from `UserDict` to subclass a dict. – AKX Oct 04 '21 at 16:25
yep, probably inheriting from dict it's just easier – ale-cci Oct 04 '21 at 16:34

Populate Python dictionaries with pre-assigned keys and values of a particular length

2 Answers2