什么是加之间的差异，在python追加为列表操作？ [英] What's the difference between plus and append in python for list manipulation?

问题描述

可能重复：结果
  <一href=\"http://stackoverflow.com/questions/2022031/python-append-vs-operator-on-lists-why-do-these-give-different-results\">Python追加（）与+运算符的列表，为什么这些给出不同的结果？

什么是Python中？

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

推荐答案

有两个主要区别。首先是 + 是比接近的含义 .extend .append ：

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]

另外，比较突出的，不同之处在于方法的工作就地： .extend 其实像 + = - 事实上，它具有完全相同的行为， + = ，但它可以接受任何可迭代的，而 + = 只能采取另一个列表。

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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