[Python-ideas] Introducing where clauses

Ben Finney ben+python at benfinney.id.au
Tue Jun 23 01:01:09 CEST 2009

Terry Reedy <tjreedy at udel.edu> writes:

> >> [(y, y) for y in (f(x) for x in some_iterable) if y < 2]
> Though I would probably write the reusable generator
> I might write this as
> ygen = (f(x) for x in some_iterable)
> # or map(f, some_iterable) if f is an existing function
> ypairs = ((y, y) for y in ygen if y < 2)
> There are really two ideas:
> map f to some_iterable
> make pairs conditionally.
> There should be no shame in putting each in a separate statement.

Indeed. My only point with the above example is that, for those who
*are* desperate to have this all as a single readable statement, the
existing syntax supports it nicely.

Since the existing syntax already easily supports every case where the
proposed syntax would be used, the burden is on those proposing the new
syntax to demonstrate benefits significant enough to outweigh the costs
of adding bulk to the language.

AFAICT, no convincingly significant benefit has been presented to add
syntax for this case.

> > I give strong emphasis on that fact, that where-clause is only
> > syntactic sugar, suggested for better readability.
> Too much sugar = stomach ache ;-).


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Ben Finney

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