my_list = [888, 666, 123, -233, 250, 13, 250, -222] last_index = len(my_list) - 1 - my_list[::-1].index(250) print(last_index)
时间: 2024-05-24 12:12:16 浏览: 14
The output of this code would be:
6
Explanation:
- The list "my_list" contains some integers.
- The expression "len(my_list) - 1" gives the index of the last element in the list.
- The expression "my_list[::-1].index(250)" gives the index of the last occurrence of the value 250 in the reversed list. The "[::-1]" syntax is used to reverse the list.
- The variable "last_index" is assigned the value of the index of the last occurrence of 250, counted from the end of the list.
- The value of "last_index" is printed, which is 6. This means that the last occurrence of the value 250 is at index 6 (counting from 0) in the original list.
相关问题
my_list = [888, 666,123,-233,250,13,250,-222 , ]last_index = len(my_list) - 1 - my_list[::-1].index(250)print(last_index)
The output of this code will be:
6
Explanation:
- The list "my_list" contains a sequence of integers.
- The variable "last_index" is initialized to the index of the last element in the list (which is the length of the list minus 1).
- The expression "my_list[::-1]" creates a reversed copy of the list.
- The method "index(250)" is called on the reversed list to find the index of the first occurrence of the integer "250" in the reversed list.
- Since the reversed list is a copy of the original list but in reverse order, the index of the first occurrence of "250" in the reversed list corresponds to the index of the last occurrence of "250" in the original list.
- Finally, the value of "last_index" is updated by subtracting the index of the last occurrence of "250" from the total length minus 1.
- The final result is that "last_index" contains the index of the last occurrence of "250" in the original list.
假如i=0,那么 my_list = my_list,否则 my_list = my_list[1:],怎么写
你可以使用条件表达式来根据`i`的值选择不同的赋值方式。具体代码如下:
```python
my_list = [1, 2, 3, 4, 5] # 原始列表
for i in range(len(my_list)):
print(my_list) # 输出当前的列表
my_list = my_list if i == 0 else my_list[1:] # 根据 i 的值选择不同的赋值方式
```
在这段代码中,`my_list if i == 0 else my_list[1:]`表示如果`i`等于0,则直接将`my_list`赋值给`my_list`,否则将`my_list`的切片赋值给`my_list`。这样,在第一次循环时,`my_list`不会发生变化,而在之后的循环中,`my_list`会去掉头一个数字。
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