the moderators are sleeping on the job :)
anyway.
> Note that of the continue cases you offer, all of them are merely simple
> if condition
yes, i said that explicitly, did you *read* my mail?
but i also said it's not always possible. you *can't* always tell prior to doing something
that it's bound to fail. you may have os.path.isfile , but not an arbitrary
"is_this_going_to_fail(x)"
and doing
> [1.0 / x for x in y if z(x != 0)]
is quite an awkward way to say "break"...
if then_break(cond)
instead of
if cond then break
- - - - -
anyway, i guess my friend may have better show-cases, as he's the one who found the
need for it. i just thought i should bring this up here. if you think better show cases
would convince you, i can ask him.
> If you couldn't guess; -1, you can get equivalent behavior without
> complicating the generator _expression_/list comprension syntax.
so how come list comprehensions aren't just a "complication to the syntax"?
you can always do them the old way,
x = []
for ....:
x.append(...)
but i since people find {shorter / more to-the-point / convenience} reason enough to
have introduced the list-comprehension syntax in the first place, there's also a case
for adding exception handling to it.
if the above snippet deserves a unique syntax, why not extend it to cover this as well?
x = []
for ....:
try:
x.append(...)
except:
...
and it's such a big syntactic change.
don't worry, i'm not going to argue it past this.
-tomer
On 4/26/06, Josiah Carlson <[EMAIL PROTECTED]> wrote:
"tomer filiba" <[EMAIL PROTECTED]> wrote:
> "[" <expr> for <expr> in <expr> [if <cond>] [except
> <exception-class-or-tuple>: <action>] "]"
Note that of the continue cases you offer, all of them are merely simple
if condition (though the file example could use a better test than
os.path.isfile).
[x for x in a if x.startswith("y") except AttributeError: continue]
[x for x in a if hasattr(x, 'startswith') and x.startswith("y")]
[1.0 / x for x in y except ZeroDivisionError: continue]
[1.0 / x for x in y if x != 0]
[open(filename) for filename in filelist except IOError: continue]
[open(filename) for filename in filelist if os.path.isfile(filename)]
The break case can be implemented with particular kind of instance
object, though doesn't have the short-circuiting behavior...
class StopWhenFalse:
def __init__(self):
self.t = 1
def __call__(self, t):
if not t:
self.t = 0
return 0
return self.t
z = StopWhenFalse()
Assuming you create a new instance z of StopWhenFalse before doing the
list comprehensions...
[x for x in a if z(hasattr(x, 'startswith') and x.startswith("y"))]
[1.0 / x for x in y if z(x != 0)]
[open(filename) for filename in filelist if z(os.path.isfile(filename))]
If you couldn't guess; -1, you can get equivalent behavior without
complicating the generator _expression_/list comprension syntax.
- Josiah
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