Simple "one-shot" writer. Opens <astr_fileName>
    and saves <astr_val> to file, then closes
    file.

def file_writeOnce(astr_fileName, astr_val, **kwargs):
    '''
    Simple "one-shot" writer. Opens <astr_fileName>
    and saves <astr_val> to file, then closes
    file.
    '''

    _str_mode = 'w'
    for key, val in kwargs.items():
        if key == 'mode':   _str_mode   = val

    FILE = open(astr_fileName, _str_mode)
    FILE.write(astr_val)
    FILE.close()