# Pre-PEP: Unpacking in Comprehensions

**URL:** <https://discuss.python.org/t/pre-pep-unpacking-in-comprehensions/96362>\
**Category:** Ideas\
**Created:** [June 22, 2025, 5:51pm UTC](https://discuss.python.org/t/pre-pep-unpacking-in-comprehensions/96362 "2025-06-22T17:51:34Z")\
**Posts on this page:** 1\
**Showing post:** 8

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**Author:** ![adqm](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/adqm/32/28615_2.png) [@adqm](https://discuss.python.org/u/adqm)\
**Post date:** [June 23, 2025, 2:05am UTC](https://discuss.python.org/t/pre-pep-unpacking-in-comprehensions/96362/8 "2025-06-23T02:05:17Z")

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> [@jorenham](#):
>
> Will this also work for PEP 530 async comprehensions?

That’s the intention, yes. I can add some words to that effect to the PEP.

> [@blhsing](#):
>
> That said, I think the PEP needs to address the [concerns](https://peps.python.org/pep-0448/#variations) raised by the explanations of why such a feature wasn’t included the PEP-448, specifically that it would cause ambiguity when unpacking in a generator expression in a call since argument list already supports unpacking.

That’s a good point. It may take a little while to find the right specific words to add to the PEP, but I can give the short version of my personal reasoning here, which is that if we’re expanding the definition of what a generator expression is, then the way to remain consistent with Python’s existing behavior (where `f(x for x in it)` passes a single argument to `f`) would be for `f(*x for x in it)` to be equivalent to `f((*x for x in it))`. That is, it seems to me like `f(<some valid generator expression>)` should always pass that generator as a single argument.

Further unpacking that generator to separate arguments to `f` could still be accomplished with `f(*(*x for x in it))`, which is perhaps a little clunky but is, I think, the way to remain consistent with what we already have.

A little bit of support in this direction, perhaps, comes from the way that the syntax error for `f(*x for x in it)` is reported in 3.13, which suggests that this is interpreted as `f(<a single malformed generator expression>)` rather than as `f(*<something>)`:

```python
>>> f(*x for x in its)
  File "<python-input-0>", line 1
    f(*x for x in its)
      ^^
SyntaxError: iterable unpacking cannot be used in comprehension

```

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