python - Python加号运算符不一致

Question

In [26]: l=[]

In [27]: s="asdsad"

In [28]: l+=s

In [29]: l
Out[29]: ['a', 's', 'd', 's', 'a', 'd']

但是，

In [30]: l+s
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

/home/xiaohan/code/proteincrawler/id_crawler.py in <module>()
----> 1 
      2 
      3 
      4 
      5 

TypeError: can only concatenate list (not "str") to list

因此，'+=' 和 '+' 中的 + 运算符是不同的。

但我觉得应该是一样的，因为都是plus

是我错了还是幕后发生了什么？

Answer 1

这解释了here .从链接复制:

It's because the += operator is doing the equivalent of calling the extend method, which treats its argument as a generic sequence, and doesn't enforce type.