Populating a list of lists with random items

Question

I have a list of lists with a certain range:

l = [["this", "is", "a"], ["list", "of"], ["lists", "that", "i", "want"], ["to", "copy"]]

And a list of words:

words = ["lorem", "ipsum", "dolor", "sit", "amet", "id", "sint", "risus", "per", "ut", "enim", "velit", "nunc", "ultricies"]

I need to create an exact replica of the list of lists, but with random terms picked from the other list.

This was the first thing that came to mind, but no dice.

for random.choice in words: for x in list: for y in x: y = random.choice

Any ideas? Thank you in advance!

Please show your two input lists, plus some sample output. Right now it's a little difficult to understand what you want to do. — Aran-Fey
– Aran-Fey, Commented Jul 6, 2017 at 16:58
you do realize that == is an equality check, not an assignment, right? — C8H10N4O2
– C8H10N4O2, Commented Jul 6, 2017 at 17:01
Do you mean you want to shuffle your list? If you pick random items from your original list, and put them in another lists, it sounds like they will not be exact replicas. — Chris
– Chris, Commented Jul 6, 2017 at 17:01

Mike Müller · Accepted Answer · 2017-07-06 17:22:40Z

You can use list comprehensions for this:

import random my_list = [[1, 2, 3], [5, 6]] words = ['hello', 'Python'] new_list = [[random.choice(words) for y in x] for x in my_list] print(new_list)

Output:

[['Python', 'Python', 'hello'], ['Python', 'hello']]

This is equivalent to:

new_list = [] for x in my_list: subl = [] for y in x: subl.append(random.choice(words)) new_list.append(subl)

With your example data:

my_list = [['this', 'is', 'a'], ['list', 'of'], ['lists', 'that', 'i', 'want'], ['to', 'copy']] words = ['lorem', 'ipsum', 'dolor', 'sit', 'amet', 'id', 'sint', 'risus', 'per', 'ut', 'enim', 'velit', 'nunc', 'ultricies'] new_list = [[random.choice(words) for y in x] for x in my_list] print(new_list)

Output:

[['enim', 'risus', 'sint'], ['dolor', 'lorem'], ['sint', 'nunc', 'ut', 'lorem'], ['ipsum', 'amet']]

Thanks Mike, works like a charm. I had the right direction, but with poor execution :)

Ben Stobbs · Accepted Answer · 2017-07-06 17:03:02Z

You're not storing the values back into your lists. Try:

for i in range(0, len(list)): subl = list[i] for n in range(0, len(subl)): list[i][n] = random.choice(words)

keredson · Accepted Answer · 2017-07-06 17:17:35Z

You should flatten your list of lists, then shuffle, then rebuild. Example:

import random def super_shuffle(lol): sublist_lengths = [len(sublist) for sublist in lol] flat = [item for sublist in lol for item in sublist] random.shuffle(flat) pos = 0 shuffled_lol = [] for length in sublist_lengths: shuffled_lol.append(flat[pos:pos+length]) pos += length return shuffled_lol print super_shuffle([[1,2,3,4],[5,6,7],[8,9]])

Prints:

[[7, 8, 5, 6], [9, 1, 3], [2, 4]]

This randomizes across ALL the lists, not just within a single sublist and guarantees no dups.

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