On Thu, Apr 01, 2010 at 11:54:53AM -0700, Bruce Leban wrote:

foo is in bar     = hasattr(foo,bar)

foo is in bar

is currently a valid and widely used expression. It means bar.__contains__(foo).

Oleg.

On Thu, Apr 01, 2010 at 03:06:18PM -0500, Robert Kern wrote:

On 2010-04-01 14:04 PM, Oleg Broytman wrote:

...

On Thu, Apr 01, 2010 at 11:54:53AM -0700, Bruce Leban wrote:

...

 foo is in bar     = hasattr(foo,bar)

foo is in bar

is currently a valid and widely used expression. It means bar.__contains__(foo).

No, it's not.

...

...

...

1 is in range(5)

File "<stdin>", line 1 1 is in range(5) ^ SyntaxError: invalid syntax

Ah, sorry, you are right. But that shows why the proposed syntax is bad - it's too similar to an existing one.

Oleg.

I'm new to the list, so give me some time to grok why "new statement/keyword" is a Bad Idea. I'll refrain from the usual, "It's just a new statement, what's so bad about that" so you guys don't have to scold me. I suspect the reason relates to bloating the core language :D

I think the in statement already hooks into __contains__. So I don't think using "foo is in bar" would work. That already exists and means something else.

I forgot about the try / catch approach. I will use this, as I think it's more Pythonic?

As far as using class, from, or with; overloading existing keywords seems a bit dangerous.

At this point and the more I think about it, I feel pretty convinced it's a bad idea.

On Apr 1, 2010, at 1:54 PM, Bruce Leban wrote:

I think this is a great idea, but I would not want to introduce a new keyword. How about

foo is in bar     = hasattr(foo,bar)
foo is not in bar = not hasattr(foo,bar)

But there are other common checks I do all the time that I would really like to have shortcuts for. Here are ways to do them without new keywords:

foo is class bar = isinstance(foo,bar)
foo is from bar  = issubclass(foo,bar)
foo is with bar  = type(foo) == type(bar)

Can we make an exception to the moratorium, just for today?

--- Bruce http://www.vroospeak.com

On Thu, Apr 1, 2010 at 8:15 AM, Robert Madole robmadole@gmail.com wrote: So I just wrote my 1-gazillionth "if hasattr('method', my_object):" and wanted badly to write this.

   if 'method' on my_object:

I'm not the most experienced Python user, but as far as I can tell hasattr is the preferred way of checking if a method exists.

Please correct me if there is a better way, otherwise I'd like to see what everyone thinks about an "on" statement being added to the Python language.

Thanks,

Rob Madole _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

On Thu, Apr 1, 2010 at 8:54 PM, Bruce Leban bruce@leapyear.org wrote:

I think this is a great idea, but I would not want to introduce a new keyword. How about     foo is in bar     = hasattr(foo,bar)     foo is not in bar = not hasattr(foo,bar) But there are other common checks I do all the time that I would really like to have shortcuts for. Here are ways to do them without new keywords:     foo is class bar = isinstance(foo,bar)     foo is from bar  = issubclass(foo,bar)     foo is with bar  = type(foo) == type(bar) Can we make an exception to the moratorium, just for today?

I hope so! I'm tossing in a few more suggestions that would make some idioms more intuitive:

* iterable except for item := (x for x in iterable if x!=item)

* pass from iterable := for i in iterable: pass

* global return value := sys.exit(value)

* import obj in module as name

import module setattr(module, name, obj) del module

* not raise: BLOCK

try: BLOCK except: pass

* with x as is: BLOCK

_x = deepcopy(x) try: BLOCK finally: x = _x; del _x

* try for i in iterable: BLOCK1 else: BLOCK2

for i in iterable: try: BLOCK1; break except: pass else: BLOCK2

George

George Sakkis, 01.04.2010 22:54:

• with x as is: BLOCK

  _x = deepcopy(x) try: BLOCK finally: x = _x; del _x

I think this use case is important enough to implement it immediately. However, since the moratorium is currently in place for Python, would it be ok to fork Python 3 to integrate it into the language? I propose Mython as the name of the fork. I also propose to drop the entire Subversion history, so that we can start using Mercurial instantaneously. That will greatly improve the freedom of Mython as a language.

Stefan

Bruce Leban wrote:

foo is in bar     = hasattr(foo,bar)
foo is not in bar = not hasattr(foo,bar)
foo is class bar = isinstance(foo,bar)
foo is from bar  = issubclass(foo,bar)
foo is with bar  = type(foo) == type(bar)

+1. Also we must absolutely have

foo is totally bar

for those *$&@*&(*@& moments we all experience while coding.