CODEWITHSUNDEEP
pythonarrayspython-2.7random
Thom Ernst
Thom Ernst

Reputation: 409

How to find item index after selecting randomized item from array

Trying to get something to work where I randomize 4 objects in an array and randomly select one of those. I need to be able to get the original index number for that chosen object back. Any idea on how I should write this as short as possible?

arrayRandomSongs = []
arrayChosen = []
trackChosen = ""

def randomizeArray(self):
    del self.arrayRandomSongs[:] # wipes array of all contents without making a new one
    self.arrayRandomSongs = self.arraySongs[:]
    random.shuffle(self.arrayRandomSongs)

def chooseListing(self):
    del self.arrayChosen[:] # same here
    for i in xrange(4):
        self.arrayChosen.append(self.arrayRandomSongs[i])
    del self.arrayRandomSongs[0:3]

def chooseTrack(self):
    self.trackChosen = random.choice(self.arrayChosen)

As you can see I would like to select the arayChosen index number for the trackChosen object, but since it's randomized I don't see how I could do that.

Upvotes: 0

Views: 69

Answers (2)

Afaq
Afaq

Reputation: 1155

You will have to keep track of indexes before randomizing. Then access the index value from the tracking list after randomizing and selecting an element from the randomized list.

For getting index of an element in list you can do <list>.index(<element>).

Explanation:

Create a copy of arrayRandomSongs before shuffling its elements.

original_arrayRandomSongs = arrayRandomSongs[:]

After getting the value of trackChosen by doing random.choice, use that value to get its index in original list by doing

original_arrayRandomSongs.index(self.trackChosen)

Upvotes: 2

Giannis Spiliopoulos
Giannis Spiliopoulos

Reputation: 2698

Well you could do something like this

list = [4,1,3,2]
list_with_indices = [(num,i) for i, num in enumerate(list)]
shuffle(list_with_indices)

essentially you keep track of the original index.

Upvotes: 1

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