Making list of number with integers and moving them Python 2.7

Question

I'm trying to make integers containing within value to shift from leftmost to rightmost. For example if values is [1,2,3,4,5] after running the code it would be [2,3,4,5,1].

I managed to write the code but I some how made the value shift from rightmost to leftmost which is other way around. Like [5,1,2,3,4]. Been sitting for hours trying to figure it out, any hands? Thank you

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

temp = values[len(values) - 1]
for index in range(len(values) - 1, 0, -1):
    values[index] = values[index - 1]
values[0] = temp

print values

Are you sure you're not lying and that code is actually from [**here**](http://www.acdict.edu.au/documents/NoviceProgrammersCorney.pdf)? — Stefan Pochmann, May 31 '16 at 01:59
@StefanPochmann, that code is quite common for this sort of problem. — RoadRunner, May 31 '16 at 04:13
@RoadRunner Well, I had googled the `for index...` line and Google found exactly one hit, the one I showed. And it's byte-for-byte the exact same four lines. But the original and main reason I call BS is that there's no way they wrote the above version and *"for hours"* unsuccessfully tried to write the other direction, as that works exactly the same (and actually is slightly simpler, as `range` upwards is nicer). — Stefan Pochmann, May 31 '16 at 12:39
Yeah that's true. I said that it's quite common because I have pretty much the same code in my database. Oh well. I hope he figured it out I guess. It's just the way you commented, I found it hilarious. — RoadRunner, May 31 '16 at 13:08

score 2 · Answer 1 · answered May 31 '16 at 01:58

2

In your case, knowing the length of the list is not necessary.

You can just use list slicing:

values[1:] + values[:1]

Example:

In [8]: values = [1,2,3,4,5]

In [9]: values[1:] + values[:1]
Out[9]: [2, 3, 4, 5, 1]

answered May 31 '16 at 01:58

heemayl

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user2390182 · Accepted Answer · 2016-05-31T13:51:48.340

This kind of rotation is most easily implemented using slice concatenation:

def rotate(lst, n):
    n = n % len(lst)  # allows rotations beyond length
    return lst[n:] + lst[:n]

> rotate([1,2,3,4,5], 1)  # rotate forward
[2, 3, 4, 5, 1]

> rotate([1,2,3,4,5], -2)  # rotate backward
[4, 5, 1, 2, 3]

Repairing your original code, however:

temp = values[0]  # store the first value cause it'll be overwritten in loop
for index in range(len(values) - 1):
    values[index] = values[index + 1]  # shift values to the left
values[len(values) - 1] = temp  # write former first to last

score 0 · Answer 3 · answered May 31 '16 at 03:07

You could cycle through the list using mutability, like this:

    def cycle(input_list):
        list_copy = input_list[:]
        list_copy.append(list_copy.pop(0))
        return list_copy

    # Output
    >>> input_ist = [i for i in range(1, 6)]   # Same as [1,2,3,4,5]
    >>> cycle(input_list)
    [2, 3, 4, 5, 1]

Making list of number with integers and moving them Python 2.7

3 Answers3