[英]Python list and tuple Unpacking
thanks for answering me at the first.. I have a List or a Tuple in Python;感谢您首先回答我。我在 Python 中有一个列表或元组; try to unpack instead of index like below:
尝试解压缩而不是像下面这样的索引:
list1 = [1,2,3,4]
first,second,third,fourth = list1
now its ok if I use it like this:现在可以了,如果我这样使用它:
first
====> it will return 1first
====> 它将返回1
but when I use it inside [ ] its like below:但是当我在 [ ] 中使用它时,如下所示:
list1[first]
====> it will return 2list1[first]
====> 它将返回2
seams it wont count [0] index in this mod!!接缝它不会在这个 mod 中计算 [0] 索引!! why?
为什么? and how to fix?
以及如何解决?
first
is set to 1, so normal to get the second element of the list. first
设置为 1,所以正常获取列表的第二个元素。 If first
was set to 'spam' for instance, list1[first]
would just fail:例如,如果
first
设置为“垃圾邮件”,则list1[first]
将失败:
>>> list1 = ["spam", "egg"]
>>> first, second = list1
>>> list1[first]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: list indices must be integers or slices, not str
I suggest using a dict
instead:我建议改用
dict
:
>>> dict1 = {"first": 1, "second": 2}
>>> dict1["first"]
1
因为first持有整数1,所以list1[first]实际上就是list1[1]
如果您希望将list1
的值用作基于 1 的索引但不想更改list1
,则可以使用(例如):
list1[first-1]
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