ARR.py

from random import randint


class ARR(object):
    def __init__(self):
        self.arr = []
        self.pos = {}
        self.len = 0

    def append(self, a):
        self.arr.append(a)
        self.pos[a] = self.len
        self.len += 1

    def remove(self, a):
        i = self.pos.pop(a)
        self.arr[i] = self.arr[-1]
        self.pos[self.arr[i]] = i
        self.len -= 1

    def random(self):
        return self.arr[randint(0, self.len - 1)]


ds = ARR()
for i in xrange(10):
    ds.append(i)
ds.append(32)
ds.remove(32)
print ds.random()