This comes up pretty often. Every example can be replaced by a loop over a single item list. It's a bit idiomatic, but not difficult. Many, as you note, can use the new walrus operator instead. [price for price in [item.get('price')] for item in basket if price is not None] On Mon, Jul 15, 2019 at 10:21 AM Fabrizio Messina <zauddelig@gmail.com> wrote:

Hello,

It is likely not the first time such a proposal is being made but let's see. I would like to explicitly set variable names in list comprehensions using a where keyword, eventually set after the if keyword:

[price for item in basket if price is not None where price := item.get( 'price')]

For this example one could use the walrus operator which is indeed smaller: [price for item in basket if price := item.get('price') is not None]

But I fell that this approach is a bit opportunistic as one is doing two things at a time, if you allow me more lines for a somewhat more complex example:

[ price * (1 + vat) for item in basket if price is not None where price := item.get('price') vat := get_vat(item, user) ]

Now this example may look pretty stupid and probably one may simply use for loop, but I feel that this kind of Haskell-like where inside of list comprehension will let the programmer have a space where they can explicitly state the variables.

Best regards, Fabrizio _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-leave@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/AHI6NI... Code of Conduct: http://python.org/psf/codeofconduct/

-- Keeping medicines from the bloodstreams of the sick; food from the bellies of the hungry; books from the hands of the uneducated; technology from the underdeveloped; and putting advocates of freedom in prisons. Intellectual property is to the 21st century what the slave trade was to the 16th.