Discard behavior when iterating over SortedSet

[gboeer]

Hi, I was wondering about the following behavior when iterating over the values of a SortedSet and discarding them, i.e. why are there still values left after this operation, and why is only each second element returned in this loop?

Another thing I was wondering is why is the sort function called twice for each value, during initialization, and also why is the sort function called at all when discarding a value?

Greetings, and thanks for the module.

def sort_val(val):
    print("sort:", val)
    return val

print("Initialize")
sorted_set = SortedSet(key=sort_val)
sorted_set.update(range(5))
print("Iterate")
for v in sorted_set:
    print("discard:", v)
    sorted_set.discard(v)
print("Finish")
print(sorted_set)

Returns:

Initialize
sort: 0
sort: 1
sort: 2
sort: 3
sort: 4
sort: 0
sort: 1
sort: 2
sort: 3
sort: 4
Iterate
discard: 0
sort: 0
discard: 2
sort: 2
discard: 4
sort: 4
Finish
SortedSet([1, 3], key=<function sort_val at 0x7f3564ffe200>)