[Python-ideas] Combining test and assignment (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Sun Jan 22 13:37:40 CET 2012

On Sun, Jan 22, 2012 at 10:04 PM, Paul Moore <p.f.moore at gmail.com> wrote:

On 22 January 2012 04:51, Steven D'Aprano <steve at pearwood.info> wrote:

Assignment as an expression feels unnatural to me:

if spam() as x != 'ham':  frobulate(x) doesn't really correspond to any natural English order. While in general I agree with you, there is a natural reading of this: "if spam() isn't 'ham', frobulate it"

Yeah, I agree characterising embedded assignments as a more formal equivalent of natural language pronouns is a useful way to think about them.

However, one of the other reasons that these proposals tend not to go anywhere is that they ultimately boil down to some people hating the idea of having to write something they personally think of as one operation as a sequence of operations instead. Like multi-line lambdas, adding embedded assignments doesn't really increase the power and expressivity of the language as a whole all that much - it just moves the dividing line between what can be cleanly expressed in a single statement and what must be expressed as multiple statements a bit.

Embedded assignments do address some instances of the loop-and-a-half problem, but even there, the more general idiom of "while True:" + "if exit_cond: break" can handle the situation quite happily.

Cheers, Nick.

-- Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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