获取其中包含双空格的字符串值

def find_double_space_string(input_string):
    double_space_strings = []
    for i in range(len(input_string) - 1):
        if input_string[i] == ' ' and input_string[i+1] == ' ':
            start_index = i
            end_index = i + 2
            while end_index < len(input_string) and input_string[end_index] == ' ':
                end_index += 1
            double_space_strings.append(input_string[start_index:end_index])
    return double_space_strings

# 示例输入字符串
input_string = "This  is a  test  string."

# 调用函数查找包含双空格的字符串值
result = find_double_space_string(input_string)

# 输出结果
for string_value in result:
    print(string_value)

  is
  test