CODEWITHSUNDEEP
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Brown Caveman-Hudson Mbong
Brown Caveman-Hudson Mbong

Reputation: 67

Interpreting Python List Output

I am having a hard time understanding why the output of this Python code is 1. Just to add, I am just new to programming:

What is the output of the following snippet:

lst = [3, 1, -2]
print(lst[lst[-1]])

Upvotes: 1

Views: 152

Answers (2)

Ashwathama
Ashwathama

Reputation: 86

The negative indexing starts from where the array ends. This means that the last element of the array is the first element in the negative indexing which is -1.

arr = [1, 2, 3, 4, 5]
print (arr[-1]) # output 5 
print (arr[-2])  #output 4
#arr[-3] =3
print(arr[arr[-3]]) #output 4

Upvotes: 1

Jaroslav Bezděk
Jaroslav Bezděk

Reputation: 7625

As @Chris mentioned in comments, lst[-1] is equal to -2, so from lst[lst[-1]] becomes lst[-2]. This code picks the second item from back.

Actually, there are always two indices for one item in lists in Python. I hope this schema will help you to better understand:

 0  1   2
 ↓  ↓   ↓
[3, 1, -2]
 ↑  ↑   ↑
-3 -2  -1

Here you can find a The Basics of Indexing and Slicing Python Lists tutorial.

Upvotes: 1

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