Randomly select values from list but with character length restriction

Question

I have a two lists of strings like the following:

test1 = ["abc", "abcdef", "abcedfhi"]

test2 = ["The", "silver", "proposes", "the", "blushing", "number", "burst", "explores", "the", "fast", "iron", "impossible"]

The second list is longer, so I want to downsample it to the length of the first list by randomly sampling.

def downsample(data):
    min_len = min(len(x) for x in data)
    return [random.sample(x, min_len) for x in data]

downsample([list1, list2])

However, I want to add a restriction that the words chosen from the second list must match the length distribution of the first list. So for the first word that is randomly chosen, it must be of the same length as the first word of the shorter list. The issue here is that replacement is not allowed either.

How can I randomly select n (length of shorter list) elements from test2 which matches the character length distribution of test1? Thanks, Jack

Answer 1

Setup

from collections import defaultdict
import random
dct = defaultdict(list)
l1 = ["abc", "abcdef", "abcedfhi"]
l2 = ["The", "silver", "proposes", "the", "blushing", "number", "burst", "explores", "the", "fast", "iron", "impossible"]

First, use collections.defaultdict to create a dictionary where the key is word length:

for word in l2:
  dct[len(word)].append(word)

# Result
defaultdict(<class 'list'>, {3: ['The', 'the', 'the'], 6: ['silver', 'number'], 8: ['proposes', 'blushing', 'explores'], 5: ['burst'], 4: ['fast', 'iron'], 10: ['impossible']})

Then you may use a simple list comprehension along with random.choice to select a random word that matches the length of each element in your first list. If a word length is not found in your dictionary, fill with -1:

final = [random.choice(dct.get(len(w), [-1])) for w in l1]

# Output
['The', 'silver', 'blushing']

Edit based on clarified requirements
Here is an approach that fulfills the requirements of not allowing duplicates if a duplicate does not exist in list 2:

for word in l2:
    dct[len(word)].append(word)

for k in dct:
    random.shuffle(dct[k])

final = [dct[len(w)].pop() for w in l1]
# ['The', 'silver', 'proposes']

This approach will raise an IndexError if not enough words exist in the second list to fulfill the distribution.