.“”部分有什么作用
''表示一个空字符串，它将被用作分隔符以将集合元素连接成字符串（一些示例可以在here中找到）
为什么结尾有个，2？
来自int文档：

类整数（x=0）
类整数（x，基数=10）

返回由数字或字符串x构造的整数对象
在这种情况下，它会将以二进制格式提供的字符串（即以2为基数）解析为int。

我希望下面的解释能有所帮助：

def flippingBits(n):
  seq = format(n, '032b')  # change the format from base 10 to base 2 with 32bit size unsigned integer into string
  return int(''.join(['0' if bit == '1' else '1' for bit in seq]), 2)
# ['0' if bit == '1' else '1' for bit in seq]  => means: build a list of characters from "seq" string
# in which whenever there is 1 convert it to 0, and to 1 otherwise; then
# ''.join(char_list) => means: build string by joining characters in char_list
# without space between them ('' means empty delimiter); then
# int(num_string, 2) => convert num_string from string to integer in a base 2

请注意，您可以使用逐位运算进行位翻转，而无需来回转换为字符串。

def flippingBits(n):
  inverted_n = ~n    # flip all bits from 0 to 1, and 1 to 0
  return inverted_n+2**32  # because the number is a signed integer, the most significant bit should be flipped as well