itertools cycle() docs question

[Terry Reedy]

On 8/21/2019 2:27 PM, Tobiah wrote:
> In the docs for itertools.cycle() there is
> a bit of equivalent code given:
> 
>      def cycle(iterable):
>          # cycle('ABCD') --> A B C D A B C D A B C D ...
>          saved = []
>          for element in iterable:
>              yield element
>              saved.append(element)
>          while saved:
>              for element in saved:
>                  yield element
> 
> 
> Is that really how it works?  Why make
> the copy of the elements?  This seems
> to be equivalent:
> 
>      def cycle(iterable):
>          while iterable:
>              for thing in iterable:
>                  yield thing

Try this experiment:

from itertools import cycle

def cycle2(iterable):
     while iterable:
         for thing in iterable:
             yield thing

for i, v in zip(range(20), cycle(i*i for i in range(4))):
     print(i, v)

for i, v in zip(range(20), cycle2(i*i for i in range(4))):
     print(i, v)

-- 
Terry Jan Reedy