[Tutor] removing items from list in for loop

[Peter Otten]

On 13/02/2022 08:52, marcus.luetolf at bluewin.ch wrote:
> Hello Experts, I am still trying to
>
> create from a list of n items, n copies of this list in a for loop with one
> item successivly removed at each iteration.


 >>> def build_lists(items):
     result = []
     for value in items:
         # copy the original list
         copy = items[:]
         # remove the current value from the copy
         copy.remove(value)
         # append to the result (a list of lists)
         result.append(copy)
     return result

 >>> build_lists(["Peter", "Paul", "Mary"])
[['Paul', 'Mary'], ['Peter', 'Mary'], ['Peter', 'Paul']]

But note a potential problem with this:

 >>> build_lists([1, 2, 1.0])
[[2, 1.0], [1, 1.0], [2, 1.0]]

You always remove the first match. If you have duplicates and want to
remove the right occurrence you need to delete rather than remove. One way:

 >>> def deleted(items, index):
	result = items[:]
	del result[index]
	return result

 >>> items = [1, 2, 1.0]
 >>> [deleted(items, i) for i in range(len(items))]
[[2, 1.0], [1, 1.0], [1, 2]]