So I'm doing py.checkio.org which is a coding game for python. My task is to reorder elements in a list. I got it working in pycharm but when i copy my solution to checkios editor I get

IndexError: list index out of range
 <listcomp>, 11
 replace_first, 11

Here's my code

from typing import Iterable


def replace_first(items: list) -> Iterable:
    lastdigit=len(items)
    if len(items) == 1:
        return items
    elif len(items) == 0:
        return items
    myorder = [1,2,3,0]
    items=[items[i] for i in myorder]
    return items


if __name__ == "__main__":
    print("Example:")
    print(list(replace_first([1, 2, 3, 4])))

    # These "asserts" are used for self-checking and not for an auto-testing
    assert list(replace_first([1, 2, 3, 4])) == [2, 3, 4, 1]
    assert list(replace_first([1])) == [1]
    assert list(replace_first([])) == []

Any idea why?

The code is not elegant in any way but I don't see why I get a index error in one editor but not the other.

CodePudding user response：

As mentioned in my comment, the code as shown will not induce IndexError. Furthermore, the implementation is overly complex and could be just:

def replace_first(items: list) -> Iterable:
  return items[1:]   items[:1]

CodePudding user response：

Possible solution is the following:

from typing import Union


def change_list_order(items: list, myorder: list) -> Union[list, str]:
    if len(items) <= 1:
        return items
    if len(items) != len(myorder):
        return f"items and myorder lists must have identical qty of elements"
    else:
        items=[items[i] for i in myorder]
        return items
    
print("Example:")
print(change_list_order([1, 2, 3, 4], [1, 2, 3, 0]))

# These "asserts" are used for self-checking and not for an auto-testing
assert change_list_order([1, 2, 3, 4], [1, 2, 3, 0]) == [2, 3, 4, 1]
assert change_list_order([1], [0]) == [1]
assert change_list_order([], [0]) == []
assert change_list_order([1, 2, 3, 4], [1, 2, 3, 0, 5]) == "items and myorder lists must have identical qty of elements"

CodePudding user response：

Never used assert, not sure about it's output, besides that, your second and third assert tried to reorder 1 item and 0 item with 4 indices. Maybe you can change myorder from myorder = [1, 2, 3, 4] to myorder = [1, 2, 3, 4][:len(item)]