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python报错TypeError: ‘NoneType‘ object is not subscriptable的解决方法

发现问题

写python的时候出现了这个错,然后网上的教程的解决方案几乎都是——“重新定义下这个变量”,看的我一脸懵逼

后来发现原来是我把return None的方法赋给了变量,之后操作变量导致的,直接上代码

  for i in range(2000):
    read_lines = random.shuffle(read_lines) # 问题出在这里了
    print(read_lines)

咋一看是没啥问题,但是一运行就报错

TypeError: 'NoneType' object is not subscriptable

后来发现原来 random.shuffle这个函数他是return None的,但是我把他赋值给了read_lines,导致后续在操作read_lines的时候一直都是这个报错,包括打印read_lines也报错

这个是random库里面的代码(看他的注释里面说的是return None)

  def shuffle(self, x, random=None):
    """
    Shuffle list x in place, and return None.

    Optional argument random is a 0-argument function returning a
    random float in [0.0, 1.0); if it is the default None, the
    standard random.random will be used.

    """

    if random is None:
      randbelow = self._randbelow
      for i in reversed(range(1, len(x))):
        # pick an element in x[:i+1] with which to exchange x[i]
        j = randbelow(i+1)
        x[i], x[j] = x[j], x[i]
    else:
      _int = int
      for i in reversed(range(1, len(x))):
        # pick an element in x[:i+1] with which to exchange x[i]
        j = _int(random() * (i+1))
        x[i], x[j] = x[j], x[i]

解决方案

把上面一行赋值语句改掉就好了

  for i in range(2000):
    random.shuffle(read_lines)
    print(read_lines)
    content_list = []

总结