python中用于列表操作的 plus 和 append 有什么区别? [英] What's the difference between plus and append in python for list manipulation?

问题描述

<块引用>

可能的重复:
Python append() 与 + 运算符在列表中，为什么这些会给出不同的结果?

Python 中列表操作的+"和append"之间的实际区别是什么?

解决方案

有两个主要区别.第一个是 + 更接近于 extend 而不是 append:

<预><代码>>>>a = [1, 2, 3]>>>一个 + 4回溯(最近一次调用最后一次):文件<pyshell#13>"，第 1 行，在 <module> 中一个 + 4类型错误:只能将列表(不是int")连接到列表>>>一个 + [4][1, 2, 3, 4]>>>a.append([4])>>>一种[1, 2, 3, [4]]>>>a.扩展([4])>>>一种[1, 2, 3, [4], 4]

另一个更突出的区别是这些方法就地工作:extend 实际上就像 += - 事实上，它的行为与+= 除了它可以接受任何迭代，而 += 只能接受另一个列表.

Possible Duplicate:
Python append() vs. + operator on lists, why do these give different results?

What is the actual difference between "+" and "append" for list manipulation in Python?

解决方案

There are two major differences. The first is that + is closer in meaning to extend than to append:

>>> a = [1, 2, 3]
>>> a + 4
Traceback (most recent call last):
  File "<pyshell#13>", line 1, in <module>
    a + 4
TypeError: can only concatenate list (not "int") to list
>>> a + [4]
[1, 2, 3, 4]
>>> a.append([4])
>>> a
[1, 2, 3, [4]]
>>> a.extend([4])
>>> a
[1, 2, 3, [4], 4]

The other, more prominent, difference is that the methods work in-place: extend is actually like += - in fact, it has exactly the same behavior as += except that it can accept any iterable, while += can only take another list.

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