How to randomly select a tuple from a list?

Question

I'm randomly creating a list of tuples from two tuples, like so:

tuple1 = ('green','yellow','blue','orange','indigo','violet')
tuple2 = ('tree',2,'horse',4,6,1,'banana')

mylist = [(t1,t2) for item1 in tuple1 for item2 in tuple2]

which of course gives me something like:

[('green','tree'),('yellow', 2)] and so on.

But then, I want to randomly select one two-item tuple from the generated mylist. In other words, return something like ('green',2).

How do I randomly select one two-item tuple from a list of them? I tried the following, but it isn't working:

my_single_tuple = random.choice(mylist.pop())

I'd be grateful for any clues or suggestions.

[EDIT] I wasn't clear about the goal: I want to remove (pop) the randomly selected tuple from the list.

the result of executing the above code: `NameError: name 't1' is not defined` — RomanPerekhrest, Dec 10 '16 at 22:31
`random.choice` takes a list, so why not just `my_single_tuple = random.choice(mylist)`? — rodrigo, Dec 10 '16 at 22:31
This should probably be `mylist = [(item1,item2) for item1 in tuple1 for item2 in tuple2]` — Philipp Braun, Dec 10 '16 at 22:32
BTW, that `mylist` can be built with `mylist = list(zip(tuple1, tuple2))` — rodrigo, Dec 10 '16 at 22:33
I made a slight edit to clarify: I want to remove the selected tuple, not just get it. — James, Dec 10 '16 at 22:37
Then randomly choose a valid index and `.pop` it. The fact that it's a tuple at that index is irrelevant. — jonrsharpe, Dec 10 '16 at 22:38
Once you have the combined list of tuples, see https://stackoverflow.com/questions/10048069/what-is-the-most-pythonic-way-to-pop-a-random-element-from-a-list to pop a random element — John Carter, Dec 10 '16 at 22:41

Philipp Braun · Accepted Answer · 2016-12-10T22:51:05.507

4

If you want to select a tuple and then remove it just get the index and remove it afterwards.

import random

tuple1 = ('green','yellow','blue','orange','indigo','violet')
tuple2 = ('tree',2,'horse',4,6,1,'banana')

mylist = [(item1,item2) for item1 in tuple1 for item2 in tuple2]


while len(mylist) > 0:
    index = random.randint(0,len(mylist)-1)
    print(mylist[index])
    del mylist[index]

edited Dec 10 '16 at 22:51

answered Dec 10 '16 at 22:41

Philipp Braun

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I said, *"that's why there's literally a `random.randrange`"*. I'm not sure what that last change was in aid of either, was there some problem with `list.pop`? Some indication that the OP wanted to clear out the list entirely and only ever print the elements in it? – jonrsharpe Dec 10 '16 at 22:50
1

Why not use random.shuffle *once* then just pop elements from the end? – Martijn Pieters Dec 11 '16 at 00:07

score 2 · Answer 2 · answered Dec 10 '16 at 22:43

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If you need to do this multiple times, just shuffle the list once and then pop items from the front:

random.shuffle(mylist)
mylist.pop()
mylist.pop()

etc.

answered Dec 10 '16 at 22:43

RemcoGerlich

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This is only valid if the original order of the list isn't useful. – jonrsharpe Dec 10 '16 at 22:45
Yes, I was thinking of the scenario where he'd pop random items from the list until the list was empty or some condition was met. – RemcoGerlich Dec 10 '16 at 22:47

score 2 · Answer 3 · answered Dec 10 '16 at 23:10

2

I think I found an answer that works:

my_item = mylist.pop(random.randrange(len(mylist)))

This successfully gives me a random tuple from the list. Thanks @philipp-braun, your answer was very close, but didn't work for me.

answered Dec 10 '16 at 23:10

James

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How to randomly select a tuple from a list?

3 Answers3