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gh-49989: Add equivalent code for the "for" statement #145067

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gh-49989: Add equivalent code for the "for" statement #145067

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25 changes: 25 additions & 0 deletions Doc/reference/compound_stmts.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -176,6 +176,31 @@ statement executed in the first suite skips the rest of the suite and continues
with the next item, or with the :keyword:`!else` clause if there is no next
item.

The following code::

for TARGET in ITER:
SUITE
else:
SUITE2

Is semantically equivalent to::

it = (ITER).__iter__()
running = True

while running:
try:
TARGET = iter.__next__()
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@StanFromIreland StanFromIreland Feb 21, 2026

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Suggested change
TARGET = iter.__next__()
TARGET = it.__next__()

You have it = (ITER).__iter__() above?

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@serhiy-storchaka serhiy-storchaka Feb 21, 2026

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Oh, I experimented with using iter() and next(), but kept explicit special methods for clarity.

On other hand, iter() is not just calling __iter__(), it works also with sequences without __iter__(), so it may be better to use it for accuracy. Then we have issue with references...

except StopIteration:
running = False
else:
SUITE
else:
SUITE2

except that implicit :ref:`special method lookup <special-lookup>` is used
for :meth:`~object.__iter__` and :meth:`~iterator.__next__`.

The for-loop makes assignments to the variables in the target list.
This overwrites all previous assignments to those variables including
those made in the suite of the for-loop::
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