如何在 Python 中创建将产生以下结果的列表 []

Question

This a question on coursera practices excess.

Create a new list using the 9th through 12th elements (four items in all) of new_lst and assign it to the variable sub_lst.

link to the question: https://runestone.academy/runestone/books/published/fopp/Sequences/TheSliceOperator.html The last question on the list.

How is my code

new_lst = ["computer", "luxurious", "basket", "crime", 0, 2.49, "institution", "slice", "sun", 
["water", "air", "fire", "earth"], "games", 2.7, "code", "java", ["birthday", "celebration", 1817, 
"party", "cake", 5], "rain", "thunderstorm", "top down"]
new_lst = new_lst[9:12]
sub_lst = new_lst
print(sub_lst)

My output:

[['water', 'air', 'fire', 'earth'], 'games', 2.7]

But here is the expected output:

['sun', ['water', 'air', 'fire', 'earth'], 'games', 2.7]

Please why am I not getting the expected output?

Answer 1

You need to start indexing at 8 as The 9th element is at index 8.

new_lst = ["computer", "luxurious", "basket", "crime", 0, 2.49, "institution", "slice", "sun", ["water", "air", "fire", "earth"], "games", 2.7, "code", "java", ["birthday", "celebration", 1817, "party", "cake", 5], "rain", "thunderstorm", "top down"]

sub_lst=new_lst[8:8+4]

Resulting output will be -

['sun', ['water', 'air', 'fire', 'earth'], 'games', 2.7]

Answer 2

你的第 9 个元素是 ['water', 'air', 'fire', 'earth'] （它被包括在内）而第 12 个元素是“代码”（它被排除在 python 中）所以结果是 [['water', '空气', '火', '地球'], '游戏', 2.7]

Answer 3

If you do a simple output of the 9th through 12th items of the list

item_count = 0
for item in new_lst:
    item_count += 1
    if 9<=item_count<=12:
        print(str(item_count)+" "+str(item))

you get the output

9 sun
10 ['water', 'air', 'fire', 'earth']
11 games
12 2.7

which is not an empty list.

To get the sub-list of the 9th through 12th items use a slice that starts at 8 based on a zero-based index and ends at 12 because the last item is not included in the output slice.

sub_lst = new_lst[8:12]

which prints as

print(sub_lst)
['sun', ['water', 'air', 'fire', 'earth'], 'games', 2.7]

Answer 4

Here is the code I executed in the link you have provided:

new_lst = ["computer", "luxurious", "basket", "crime", 0, 2.49, "institution", "slice", "sun", ["water", "air", "fire", "earth"], "games", 2.7, "code", "java", ["birthday", "celebration", 1817, "party", "cake", 5], "rain", "thunderstorm", "top down"]
sub_lst = new_lst[8:12]
print(sub_lst)

This line in the code you have written, you have updated the value of new_lst to only 4 elements.

new_lst = new_lst[9:12]

So, it is showing the expected value as [].

Answer 5

I think you are assigning more than the question asked and here is the solution

new_lst = ["computer", "luxurious", "basket", "crime", 0, 2.49, "institution", "slice", "sun", ["water", "air", "fire", "earth"], "games", 2.7, "code", "java", ["birthday", "celebration", 1817, "party", "cake", 5], "rain", "thunderstorm", "top down"]
sub_lst = new_lst[8:12]

just do "sub_lst = new_lst[8:12]" assign just sliced list in sub_lst.