[Tutor] iterate list items as lvalue

[János Juhász]

Dear All,

I would like to thanks for your responds.


Ricardo Aráoz wrote:
  Kent Johnson wrote:
  > Dave Kuhlman wrote:
  >> Consider the following:
  >>
  >>     >>> array = [1,2,3,4,5]
  >>     >>> array2 = array
  >>     >>> array = [i * 2 for i in array]
  >>     >>> array
  >>     [2, 4, 6, 8, 10]
  >>     >>> array2
  >>     [1, 2, 3, 4, 5]
  >>
  >> So, did you want array2 to change, or not?
  >>
  >> Here is a solution that changes the object that both array and
  >> array2 refer to:
  >>
  >>     >>> array = [1, 2, 3, 4, 5]
  >>     >>> array2 = array
  >>     >>> for idx, item in enumerate(array):
  >>         array[idx] = item * 2
  >>     >>> array
  >>     [2, 4, 6, 8, 10]
  >>     >>> array2
  >>     [2, 4, 6, 8, 10]
  >>
  >> Basically, this modifies the list "in place", rather than making a
  >> new list from the old one.
  > 
  > Another way to do this is to assign to a slice of array:
  > 
  > array[:] = [ item*2 for item in array ]
  > 
  > Kent
  Thanks, hadn't really thought about having a copy of array (guess I'm
  too much of a n00b). Really simple and elegant way of solving it though.

I have played the way Kent showed.

>>> array = [1, 2, 3, 4, 5]
>>> array[2] = [item+5 for item in array]
>>> array
[1, 2, [6, 7, 8, 9, 10], 4, 5]

>>> array = [1, 2, 3, 4, 5]
>>> array[2:2] = [item+5 for item in array]
>>> array
[1, 2, 6, 7, 8, 9, 10, 3, 4, 5]

Even more interesting

>>> array = [1, 2, 3, 4, 5]
>>> array[3:2] = ['new','members', 'in', 'the', 'list']
>>> array
[1, 2, 3, 'new', 'members', 'in', 'the', 'list', 4, 5]



Yours sincerely,
Janos Juhasz