How can I reverse a list in Python?

Question

How can I do the following in Python?

array = [0, 10, 20, 40]
for (i = array.length() - 1; i >= 0; i--)

I need to have the elements of a

Answer 1

You can make use of the reversed function for this as:

>>> array=[0,10,20,40]
>>> for i in reversed(array):
...     print(i)

Note that reversed(...) does not return a list. You can get a reversed list using list(reversed(array)).

Answer 2

Using some logic

Using some old school logic to practice for interviews.

Swapping numbers front to back. Using two pointers index[0] and index[last]

def reverse(array):
    n = array
    first = 0
    last = len(array) - 1
    while first < last:
      holder = n[first]
      n[first] = n[last]
      n[last] = holder
      first += 1
      last -= 1
    return n

input -> [-1 ,1, 2, 3, 4, 5, 6]
output -> [6, 1, 2, 3, 4, 5, -1]

Answer 3

Can be done using __reverse__ , which returns a generator.

>>> l = [1,2,3,4,5]
>>> for i in l.__reversed__():
...   print i
... 
5
4
3
2
1
>>>

Answer 4

use

print(reversed(list_name))

Answer 5

>>> L = [0,10,20,40]
>>> L[::-1]
[40, 20, 10, 0]

Extended slice syntax is explained well in the Python What's new Entry for release 2.3.5

By special request in a comment this is the most current slice documentation.

Answer 6

Reverse of a user input values in one line code:

for i in input()[::-1]: print(i,end='')