Python Random Function To Select A New Item From A List Of Values

I need to fetch random numbers from a list of values in Python. I tried using random.choice() function but it sometimes returns same values consecutively. I want to return new rand

Solution 1:

Create a copy of the list, shuffle it, then pop items from that one by one as you need a new random value:

shuffled = origlist[:]
random.shuffle(shuffled)

def produce_random_value():
    return shuffled.pop()

This is guaranteed to not repeat elements. You can, however, run out of numbers to pick, at which point you could copy again and re-shuffle.

To do this continuously, you could make this a generator function:

defproduce_randomly_from(items):
    whileTrue:
        shuffled = list(items)
        random.shuffle(shuffled)
        while shuffled:
            yield shuffled.pop()

then use this in a loop or grab a new value with the next() function:

random_items = produce_randomly_from(inputsequence)
# grab one random value from the sequencerandom_item = next(random_items)

Solution 2:

Here is an example:

>>>random.sample(range(10), 10)
[9, 5, 2, 0, 6, 3, 1, 8, 7, 4]

Just replace the sequence given by range with the one you want to choose from. The second number is how many samples, and should be the length of the input sequence.

Solution 3:

If you just want to avoid consecutive random values, you can try this:

import random
defnonrepeating_rand(n):
    ''' Generate random numbers in [0, n) such that no two consecutive numbers are equal. '''
    k = random.randrange(n)
    while1:
        yield k
        k2 = random.randrange(n-1)
        if k2 >= k: # Skip over the previous number
            k2 += 1
        k = k2

Test:

for i,j in zip(range(25), nonrepeating_rand(3)):
    print i,j

prints (for example)

0 1
1 0
2 2
3 0
4 2
5 0
6 2
7 1
8 0
9 1
10 0
11 2
12 0
13 1
14 0
15 2
16 1
17 0
18 2
19 1
20 0
21 2
22 1
23 2
24 0

You can use nonrepeating_rand(len(your_list)) to get random indices for your list.