Discrepancy between inplace add and add for list and iterables

Documentation

Noticed this discrepancy between inplace add and add for list and iterables, not sure if this behavior is purposefully intended or a bug:

The Addition Assignment += operator will concatenate str to list, treating the str as an iterable and behaving like list.extend(...) instead of throwing TypeError, as one might expect, since the Addition operator + throws a TypeError when attempting to concatenate str to list.

未指定源文件或测试。首先复现所附示例，这些示例比较了字符串和其他 iterable 的 list += 与 list +，然后阅读 Python 语言文档中与这些运算符相关的内容。完成的标准是确定该差异的预期行为，并找出适当的文档修改或澄清之处。