def no_esc_prefix_re(esc='\\'):

    esc_re = re.escape(esc)

    return '(?<!'+esc_re+')((?:'+esc_re+'{2})*)' # an even # of escs

def escd_char_re(escd_char, esc):

    assert escd_char != esc # not supported; use str_.replace() instead

    return no_esc_prefix_re(esc)+re.escape(escd_char)

def esc_re_map(map_):

    '''

    for use with replace_all_re()

    @param map_ [(escd_char, char), ...] # use flip_map() if needed

    @return [(escd_char_re, escd_char_re_sub), ...]

    '''

    _1st_escd_char = map_[0][0] # 1st entry > escd_char

    esc = _1st_escd_char[0] # esc char is 1st char

    return [(escd_char_re(escd_char, esc), r'\1'+char)

        for escd_char, char in map_]

def unesc_quotes(str_, quote='"', esc='\\', quote_esc=None):

    if quote_esc == None: quote_esc = esc+quote

    # can't use `.decode('string_escape')` for this because it doesn't decode

    # custom escapes, such as GWT's \! for |

    return replace_all_re(esc_re_map([(quote_esc, quote)]),

        str_).replace(esc+esc, esc)