python print 3 first elements of list in reverse mode

Question

suppose i have a list like this:

my_list = [0,1,2,3,4,5] # range(5)

i want to print this:

[2,1,0]

my python script is:

print(my_list[2:-1:-1])

but it prints an empty list!

is this a bug in python(2 and 3!)?

i wont use any trick like:

num_of_elems_i_want = 3
print(my_list[::-1][len(my_list) - num_of_elems_i_want:])

or third party modules..

Nickil Maveli · Accepted Answer · 2016-08-22 20:23:46Z

5

You could slice the list as shown:

print(my_list[2::-1])      # L[start:end:step]

EDIT :

The result that you had obtained is not a Bug.

Remember that traversal of the list elements takes place from left to right and there are no elements till end=-4[viz elements: 5 → 0 → 1 → 2] from start=2. So, an empty list is returned as a result.

For the same reason, you could also do print(my_list[2:-7:-1])

edited Aug 22, 2016 at 20:23

answered Aug 12, 2016 at 16:12

Nickil Maveli

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2 Comments

Stefan Pochmann Over a year ago

Doesn't answer the question (whether the result of the original is a bug).

pretzlstyle Over a year ago

@StefanPochmann Novice programmers with questions often assume that there is a bug in the language when they are certain their code is right. In reality, it is never a bug in the language

Frederico Martins · Accepted Answer · 2016-08-12 16:19:22Z

1

You can also invert your list permanently for other uses:

my_list.reverse()
print(my_list[-4:-1])

edited Aug 12, 2016 at 16:19

answered Aug 12, 2016 at 16:12

Frederico Martins

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