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

Use a function assuming n is the shift that is less than the length of list l like so:

shift = lambda l, n: l[-n:] + l[:-n] # i.e. shift([1, 2, 3, 4], 3)

Answer 2

If you are trying to shift the elements, use collections.deque rotate method:

#! /usr/bin/python3

from collections import deque
a = deque([1, 2, 3, 4])
a.rotate()
print(a)

Result:

[2, 3, 4, 1]

Answer 3

You can use this:

li=li[-1:]+li[:-1]

Answer 4

you can use roll function from numpy.

>>> import numpy as np
>>> q = [1, 2, 3, 4, 5]
>>> np.roll(q, 2)
array([4, 5, 1, 2, 3])

Hope it helps!

Answer 5

If you actually want to shift the elements, you can use modulo to cycle the list and reassign the elements to their shifted positions:

def shift(lst, shft=0):
    ln = len(lst)
    for i, ele in enumerate(lst[:]):
        lst[(i + shft) % ln] = ele
    return lst

In [3]: shift( ['a','b','c','d'] , 1)
Out[3]: ['d', 'a', 'b', 'c']

In [4]: shift( ['a','b','c','d'] , 2)
Out[4]: ['c', 'd', 'a', 'b']

In [5]: shift( ['a','b','c','d'] , 3)
Out[5]: ['b', 'c', 'd', 'a']

If you only want a single shift just shift the last element to the front extending the list:

def shift(lst):
    lst[0:1] = [lst.pop(),lst[0]]
    return lst

Both of which change the original list.

Answer 6

Solution for your query :

def shift(aList):
    l = list()
    n = len(aList)
    l.append(aList[-1])
    temp = aList[:n-1]
    for i in temp:
        l.append(i)
    return l
print(shift(aList=[1,2,3]))