Shift list elements to the right and shift list element at the end to the beginning

Question

I want to rotate elements in a list, e.g. - shift the list elements to the right so [\'a\',\'b\',\'c\',\'d\'] would become [\'d\',\'a\',\'b\',\'c\'], o

Answer 1

You can use negative indices together with list concatenation:

def shift(seq, n=0):
    a = n % len(seq)
    return seq[-a:] + seq[:-a]

Answer 2

The question seems to imply to me that the list itself should be modified rather than a new list created. A simple in place algorithm is therefore:

lst = [1, 2, 3, 4, 5]

e1 = lst[-1]
for i, e2 in enumerate(lst):
    lst[i], e1 = e1, e2

print(lst)

Giving:

[5, 1, 2, 3, 4]

Answer 3

If you are allergic to slice notation: a.insert(0,a.pop())

Usage:

In [15]: z=[1,2,3]

In [16]: z.insert(0,z.pop())

In [17]: z
Out[17]: [3, 1, 2]

In [18]: z.insert(0,z.pop())

In [19]: z
Out[19]: [2, 3, 1]

Answer 4

This could be done simply by using list method: insert,

values = [2, 3, 5, 7, 11, 13]

def shift(list):
    new_list = []

    for i in list:
        new_list.insert(len(new_list)-1, i)

    return new_list

print(shift(values))

Output is:

[3, 5, 7, 11, 13, 2]

Answer 5

You can just slice the last element off the list, then add it to the beginning of a new list:

aList = [aList[-1]] + aList[:-1]

Here is the result:

>>> aList = [1,2,3]
>>> aList = [aList[-1]] + aList[:-1]
>>> aList
[3, 1, 2]

Answer 6

Simple use of slice syntax:

def shift(seq):
    return [seq[-1]] + seq[:-1]

assert shift([1, 2, 3, 4, 5]) == [5, 1, 2, 3, 4]

Generalized version with changeable shift:

def shift(seq, shift=1):
    return seq[-shift:] + seq[:-shift]

assert shift([1, 2, 3, 4, 5]) == [5, 1, 2, 3, 4]
assert shift([1, 2, 3, 4, 5], 2) == [4, 5, 1, 2, 3]