Solution:

When using next() to access an iterator that has been iterated, there will be such an error: stopiteration
the solution is to give a default value: next (ITER, default) , which will be output after the iteration is completed
suppose that the original writing method of the loop is:

a = next(iter_test) # Iteration completion will report an error StopIteration
print(a)

Change to:

a = next(iter_test,None)
if a is not None:
	print(a)

Problem analysis

The following code will report an error:

iter_list = iter([1, 2, 3, 4])

for i in range(10):
    print(next(iter_list))

Error will be reported after outputting 1234, which can be changed to:

iter_list = iter([1, 2, 3, 4])

for i in range(10):
    a = next(iter_list, None)
    if a is not None:
        print(a)

This will output: 1 2 3 4