def random_pos(self, context_iterable, num_permutations):
        """Obtains random positions w/ replacement which match sequence context.

        Parameters
        ----------
        context_iterable: iterable containing two element tuple
            Records number of mutations in each context. context_iterable
            should be something like [('AA', 5), ...].
        num_permutations : int
            Number of permutations used in the permutation test.

        Returns
        -------
        position_list : list
            Contains context string and the randomly chosen positions
            for that context.
        """
        position_list = []
        for contxt, n in context_iterable:
            pos_array = self.random_context_pos(n, num_permutations, contxt)
            position_list.append([contxt, pos_array])
        return position_list