See: https://gist.github.com/panzi/8924450 But again, I don't recommend to use this. Just to demonstrate what is already possible with the most simple constructs. Am 2014-02-10 19:14, schrieb Mathias Panzenböck:

You don't need a context manger here:

switch = lambda value: lambda other: value == other

case = switch(foobar) if case(1): pass if case(2): pass

But I don't think this is at all useful. Maybe if case does something more complex than == (e.g. isinstance for classes and matching of regular expressions etc.). But than it's a bit of black magic. What if value and other both are classes or regular expressions?

Other version:

case = foobar.__eq__ if case(1): pass if case(2): pass

Am 2014-02-10 15:31, schrieb Sturla Molden:

...

I've noticed that PyExt has a switch statement implemented as a context manager.

with switch(foobar): if case(1): pass if case(2): pass

Would this be something to consider for the standard lib, e.g. contextlib?

Sturla

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It looks cooler. It also feels slightly less aggravating. On Mon, Feb 10, 2014 at 5:29 PM, Greg Ewing wrote:

Sturla Molden wrote:

...

I've noticed that PyExt has a switch statement implemented as a context manager.

with switch(foobar): if case(1): pass if case(2): pass

What advantage does this have over an if-else chain?

-- Greg

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-- Ryan If anybody ever asks me why I prefer C++ to C, my answer will be simple: "It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was nul-terminated."

Because it doesn't *look *like one. On Tue, Feb 11, 2014 at 9:25 AM, Chris Angelico wrote:

On Wed, Feb 12, 2014 at 2:22 AM, Ryan Gonzalez wrote:

...

It looks cooler. It also feels slightly less aggravating.

On Mon, Feb 10, 2014 at 5:29 PM, Greg Ewing

wrote:

...

Sturla Molden wrote:

...

I've noticed that PyExt has a switch statement implemented as a context manager.

with switch(foobar): if case(1): pass if case(2): pass

What advantage does this have over an if-else chain?

Since it fundamentally _is_ an if chain (without the elses), how does it feel less aggravating than one?

ChrisA _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/

-- Ryan If anybody ever asks me why I prefer C++ to C, my answer will be simple: "It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was nul-terminated."

On Tue, Feb 11, 2014 at 10:44 AM, Ned Batchelder wrote:

On 2/11/14 10:37 AM, Ryan Gonzalez wrote:

Because it doesn't *look *like one.

If it *is* one, it's a good thing to *look* like one.

PS: could you bottom-post? It makes it easier to follow the thread. Thanks :)

--Ned.

On Tue, Feb 11, 2014 at 9:25 AM, Chris Angelico wrote:

...

On Wed, Feb 12, 2014 at 2:22 AM, Ryan Gonzalez wrote:

...

It looks cooler. It also feels slightly less aggravating.

On Mon, Feb 10, 2014 at 5:29 PM, Greg Ewing < greg.ewing@canterbury.ac.nz> wrote:

...

Sturla Molden wrote:

...

I've noticed that PyExt has a switch statement implemented as a

context

...

...

manager.

with switch(foobar): if case(1): pass if case(2): pass

What advantage does this have over an if-else chain?

Since it fundamentally _is_ an if chain (without the elses), how does it feel less aggravating than one?

ChrisA _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/

-- Ryan If anybody ever asks me why I prefer C++ to C, my answer will be simple: "It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was nul-terminated."

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Depends on whether or not you actually like the way it looks. P.S. Sorry, GMail top-posts by default. -- Ryan If anybody ever asks me why I prefer C++ to C, my answer will be simple: "It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was nul-terminated."

C and C++ have: switch(value) { case 1: do_stuff; break; case 2: case 3: do_stuff_2(); break; default: break; } On Tue, Feb 11, 2014 at 10:58 AM, Philipp A. wrote:

2014-02-11 17:44 GMT+01:00 Ned Batchelder :

If it *is* one, it's a good thing to *look* like one.

well, you also get to remove the repeated variable name.

but a real switch statement should take advantage of python's hashing. the best we have is

def _handle_spam(): vomit() def _handle_eggs(): yum()

handlers = { 'spam': _handle_spam, 'eggs': _handle_eggs, }

handlers[food]()

which makes me _handle_spam(). ------------------------------

the problem of a real switch statement is apparently that there's no good syntax:

switch food case 'spam': ...

is strange due to the missing colon. we have that nowhere in python. yet

switch food: case 'spam': ...

is strange because after the colon, everywhere else is an indentation. but

switch food: case 'spam': ...

is indentation overkill. nobody has found a good syntax yet.

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-- Ryan If anybody ever asks me why I prefer C++ to C, my answer will be simple: "It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was nul-terminated."

Skip Montanaro wrote:

On Tue, Feb 11, 2014 at 10:58 AM, Philipp A. wrote:

...

the problem of a real switch statement is apparently that there’s no good syntax

Last time this was discussed at length, the main sticking point seemed to be that people generally expect a switch statement to be implemented by something more efficient than a series of if-tests. But that's extremely difficult to do in Python except when all of the case values are literals, which is a very special situation. So in general, any switch statement in Python would just be pure syntactic sugar for an if-else chain, and that doesn't seem to be considered enough of an advantage to bother with. -- Greg