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

With reversed and list:

>>> list1 = [1,2,3]
>>> reversed_list = list(reversed(list1))
>>> reversed_list
>>> [3, 2, 1]

Answer 2

Strictly speaking, the question is not how to return a list in reverse but rather how to reverse a list with an example list name array.

To reverse a list named "array" use array.reverse().

The incredibly useful slice method as described can also be used to reverse a list in place by defining the list as a sliced modification of itself using array = array[::-1].

Answer 3

Reversing in-place by switching references of opposite indices:

>>> l = [1,2,3,4,5,6,7]    
>>> for i in range(len(l)//2):
...     l[i], l[-1-i] = l[-1-i], l[i]
...
>>> l
[7, 6, 5, 4, 3, 2, 1]

Answer 4

For reversing the same list use:

array.reverse()

To assign reversed list into some other list use:

newArray = array[::-1] 

Answer 5

You can also use the bitwise complement of the array index to step through the array in reverse:

>>> array = [0, 10, 20, 40]
>>> [array[~i] for i, _ in enumerate(array)]
[40, 20, 10, 0]

Whatever you do, don't do it this way ;)

Answer 6

list_data = [1,2,3,4,5]
l = len(list_data)
i=l+1
rev_data = []
while l>0:
  j=i-l
  l-=1
  rev_data.append(list_data[-j])
print "After Rev:- %s" %rev_data