import itertools


def get_pwdist_indices(sequences):
    """
    From a list of sequences get lower triangle indices tuples (i,j)
    for pairwise comparisons.

    Parameters
    ----------
    sequences : list of strings
        list of (likely amino acid) strings

    Returns
    -------
    ind_tuples : list
        ist of tuples (i,j)

    """
    ind_tuples = []
    L = len(sequences)
    for i, j in itertools.product(list(range(L)), list(range(L))):
        if i <= j:
            ind_tuples.append((i, j))
    return(ind_tuples)