def unique_number_from_list(input_list):
    """
    Produce a list of integers corresponding to the number of times an
    element in the input list has been observed.

    Parameters
    ----------
    input_list : list
        list of values

    Returns
    -------
    occurrence : list
        integer list

    Examples
    --------

    unique_number_from_list(['a','a','b','c','c','c'])
    unique_number_from_list(['a','b','c'])

    """
    dups = {}
    occurrence = []
    for i, val in enumerate(input_list):
        if val not in dups:
            dups[val] = [i, 1]
        else:
            dups[val][1] += 1
        occurrence.append(dups[val][1])
    return occurrence
