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From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.python
Subject: Re: get_used_memory
Date: Mon, 15 Jun 2026 12:02:52 -0700
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Xref: csiph.com comp.lang.python:197818

Jon Ribbens <jon+usenet@unequivocal.eu> writes:
> My biggest complaint about := is the arbitrary and mysterious
> restrictions on what you can use on the left hand side. You can't
> even say "a.b := c". The PEP that introduced ":=" barely even
> mentions these restrictions, let alone discusses or explains them.

Yeah that's pretty annoying.  Haskell doesn't have destructive
assignments at all, but you can put the equivalent of match/case inside
expressions.  So, something like:
   
   fromList [(a, read b) | (a:b:_) <- words x | x <- xs] :: Map String Int

The vertical bar is like "for" in Python's list comprehensions, "read"
is like int(str) except it converts to arbitrary datatypes, "words" is
like "split", and ":: Map String Int" is a type annotation that says
it's making a dictionary mapping strings to Ints.  The Int type
signature tells "read" to convert to ints instead of floats or whatever.
Finally, (a:b:_) binds the first two elements of x.split() and throws
away the rest.

I haven't tested the above so maybe I did something dumb.  I haven't
written any Haskell in a while.