random.SystemRandom().randint() inefficient

[MRAB]

On 27/07/2022 16:43, Cecil Westerhof via Python-list wrote:
> "Michael F. Stemper" <michael.stemper at gmail.com> writes:
> 
>> This is orthogonal to your question, but might be of some use to you:
>>
>> The combination of using len(to_try) as an argument to randint() and
>> saving the output to a variable named "index" suggests that you might
>> be setting up to select a random element from to_try, as in:
>>   something = to_try[index]
>>
>> If that is the case, you might want to consider using random.choice() instead:
>>
>>   >>> from random import choice
>>   >>> to_try = [2,3,5,7,11,13,"seventeen",19]
>>   >>> choice(to_try)
>>   2
>>   >>> choice(to_try)
>>   'seventeen'
>>   >>> choice(to_try)
>>   13
>>   >>> choice(to_try)
>>   5
>>   >>>
> 
> Yes, I try to select a random element, but it has also to be removed,
> because an element should not be used more as once.
> This is the code I use:
>      # index = randbelow(len(to_try))
>      index = randrange(len(to_try))
>      found = permutation[to_try.pop(index)]
> 

When you pop an element from the last, the elements after it need to be 
moved down, which takes time.

Try shuffling the list and then popping the now randomly-ordered 
elements off the end.