Find the index of the n'th item in a list

Question

I want to find the index of the n\'th occurrence of an item in a list. e.g.,

x=[False,True,True,False,True,False,True,False,False,False,True,False,True]
         


        

Answer 1

Here is another way to find the nth occurrence of x in a list itrbl:

def nthoccur(nth,x,itrbl):
    count,index = 0,0
    while count < nth:
        if index > len(itrbl) - 1:
            return None
        elif itrbl[index] == x:
            count += 1
            index += 1
        else:
            index += 1
    return index - 1