[Python-ideas] PEP 315: do-while

[Nick Coghlan]

On 29 June 2013 00:22,  <jimjhb at aol.com> wrote:
> The takewhile syntax is kind of god awful.  The lambda thing always gives
> me pause, though I now 'grok' the whole thing to be a conditional.
> I don't think the issue is about added complexity to the comprehension
> (as the added clause would be optional anyway)

Note that this is a misunderstanding of what "added complexity" means
in a language design context. More options almost always mean more
complexity.

The only way adding more options can simplify things in a practical
sense is when they shift complexity from user code to the interpreter
implementation by extracting an existing common pattern and giving it
dedicated syntax (such as comprehensions, generator expressions and
"with" statements), or when they provide a corrected alternative to an
existing tempting-but-wrong construct (such as "a if p else b"
replacing the "p and a or b" hack and "yield from itr" replacing the
coroutine incompatible "for x in itr: yield x").

In this case, the proposal is only tinkering at the edges - you can
*always* handle it by creating a custom generator instead. All this
proposal does is subtly adjust the point at which it becomes more
attractive to write a custom generator function than it is to do the
operation in line in the comprehension or generator expression.

Cheers,
Nick.

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