def replace_fields(field_list, *pairs):
    """Given a list of field names and one or more pairs,
    replace each item named in a pair by the pair.

    fl = 'one two three'.split()
    replace_fields(fl, ('two', 'spam'))
    # ['one', ('two', 'spam'), 'three']
    """
    result = list(field_list)
    for field_name, source in pairs:
        index = field_list.index(field_name)
        result[index] = field_name, source
    return result