Re: Python's sad, unimaginative Enum
- Original Message - On Mon, 13 May 2013 13:00:36 +0200, Jean-Michel Pichavant wrote: - Original Message - That's the title of this little beast http://www.acooke.org/cute/Pythonssad0.html if anybody's interested. -- If you're using GoogleCrap™ please read this http://wiki.python.org/moin/GoogleGroupsPython. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list python 2.5 class Enum: class __metaclass__(type): def __iter__(self): for attr in sorted(dir(self)): if not attr.startswith(__): yield getattr(self, attr) class Colours(Enum): RED = red GREEN = green py class Experience(Enum): ... NOVICE = 'novice' ... GREEN = 'green' ... EXPERIENCED = 'experienced' ... MASTER = 'master' ... py py Colours.GREEN == Experience.GREEN True Oops. It's very easy to make something which does a few things that enums should do, and call it an Enum. It's much harder to do a lot of things that enums should do. -- Steven I was just proposing a solution I've been using and found quite satisfactory. As for the perfect enumness of that solution, I don't know. To be honest, I'm not sure I know the exact definition of an enum, and whether or not the C enum fits 100% that definition. It does the job in python. Some people may find it useful, others may just ignore it. Additionally, the bug you mentioned can be written in C as well, casts allow to compare apples and oranges: (Colours::GREEN == (enum Coulours::Colour)Experiences::GREEN) JM -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python's sad, unimaginative Enum
On 13 May 2013 12:05, Jean-Michel Pichavant jeanmic...@sequans.com wrote: class Enum: class __metaclass__(type): That's some cool metaclass fu! I didn't know that to be possible -- http://mail.python.org/mailman/listinfo/python-list
Re: Python's sad, unimaginative Enum
Chris Angelico於 2013年5月14日星期二UTC+8上午1時36分34秒寫道： On Mon, May 13, 2013 at 8:17 PM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Let's look at his major criticisms: 1) values aren't automatically generated. True. So what? That is the *least* important part of enums. I stopped following the -ideas threads about enums, but IIRC autogeneration of values was in quite a few of the specs early on. So you can probably find the arguments against it in the list archives. FWIW, though, I do like C's autogeneration of enum values - but use it in only a small proportion of my enums. It's not a terrible loss, but it is a loss. ChrisA Because a hash table can replace the enums in other languages, it is more pythonic to use a dictionary built first to replace the enums. I think it is the same style of programming in perl and ruby. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python's sad, unimaginative Enum
On May 14, 2:24 pm, Jean-Michel Pichavant jeanmic...@sequans.com wrote: - Original Message - On Mon, 13 May 2013 13:00:36 +0200, Jean-Michel Pichavant wrote: - Original Message - That's the title of this little beast http://www.acooke.org/cute/Pythonssad0.htmlif anybody's interested. -- If you're using GoogleCrap™ please read this http://wiki.python.org/moin/GoogleGroupsPython. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list python 2.5 class Enum: class __metaclass__(type): def __iter__(self): for attr in sorted(dir(self)): if not attr.startswith(__): yield getattr(self, attr) class Colours(Enum): RED = red GREEN = green py class Experience(Enum): ... NOVICE = 'novice' ... GREEN = 'green' ... EXPERIENCED = 'experienced' ... MASTER = 'master' ... py py Colours.GREEN == Experience.GREEN True Oops. It's very easy to make something which does a few things that enums should do, and call it an Enum. It's much harder to do a lot of things that enums should do. -- Steven I was just proposing a solution I've been using and found quite satisfactory. As for the perfect enumness of that solution, I don't know. To be honest, I'm not sure I know the exact definition of an enum, and whether or not the C enum fits 100% that definition. It does the job in python. Some people may find it useful, others may just ignore it. Additionally, the bug you mentioned can be written in C as well, casts allow to compare apples and oranges: (Colours::GREEN == (enum Coulours::Colour)Experiences::GREEN) Enums are like names. And like names are impossible to do right: http://www.kalzumeus.com/2010/06/17/falsehoods-programmers-believe-about-names/ -- http://mail.python.org/mailman/listinfo/python-list
Python's sad, unimaginative Enum
That's the title of this little beast http://www.acooke.org/cute/Pythonssad0.html if anybody's interested. -- If you're using GoogleCrap™ please read this http://wiki.python.org/moin/GoogleGroupsPython. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list
Re: Python's sad, unimaginative Enum
On Mon, 13 May 2013 10:24:40 +0100, Mark Lawrence wrote:
That's the title of this little beast
http://www.acooke.org/cute/Pythonssad0.html if anybody's interested.
Well, that's one way of looking at it. And I can't exactly *disagree*.
But... but...
In many ways, it's a dull language, borrowing solid old concepts
from many other languages styles: boring syntax, unsurprising
semantics, few automatic coercions, etc etc. But that's one of
the things I like about it. -- Tim Peters, 16 Sep 93
Being sad and unimaginative is a *good thing* when it comes to syntax.
Which would you rather read?
Python:
try:
int(astring)
except ValueError:
print(False)
APL:
⊃⎕VFI{w←⍵⋄((w='-')/w)←'¯'⋄w}
[pedant: okay, so the two code snippets are not *exactly* equivalent. So
sue me.]
Let's look at his major criticisms:
1) values aren't automatically generated.
True. So what? That is the *least* important part of enums. The most
important things about enums are:
- they aren't strings, but look like symbolic values;
- or they are ints (for compatibility with C libraries) that look like
symbolic values.
Probably half the use-cases for enums are for compatibility with C
libraries, where you *need* to specify the value. There's no point you
defining an enum SOCK_RAW, having Python decide to set it to 7, when the
rest of the world agrees it should have the value 3.
2) The enum implementation allows duplicates.
Yes, this *is* a feature. In the real world, enums are not unique. There
are aliases (maybe you want FAMILY_NAME and SURNAME to be the same enum),
and misspelled enums need to be corrected:
class Insects(Enum):
bee = 2
ant = 3
wasp = 4 # Preferred spelling.
wsap = 4 # Oops, keep this for backward compatibility!
I'm sorry for all those who can't avoid duplicating values, but really,
Python doesn't protect them from other silly typos, why are Enums so
special that they need to be treated differently?
3) the functional API for creating auto-numbered Enums suffers from the
same problems as namedtuples:
[quote]
- you need to repeat the class name (in a string, which your IDE is
unlikely to check)
- the parameters are themselves in a string, which your IDE is
unlikely to parse and provide in auto-complete (they can be separate
strings, in a sequence, but that doesn't really help).
[end quote]
Then maybe you shouldn't be relying on such a lousy IDE then.
Well, perhaps I'm being a tad harsh. After all, it's not like it is a
*feature* that namedtuple *requires* you to include the class name. But
really, it's a trivial inconvenience. Python has much worse, e.g.:
- why aren't my CONSTANTS actually constant?
and yet somehow we survive.
4) Auto-generated enums aren't strings:
[quote]
That would makes sense (red = 'red'), in that it would display
nicely and is going to provide easy to debug values. So nope.
[end quote]
Missing the point entirely. The *whole point* of enum red is that it WILL
display as 'red', even though it wraps an underlying value of whatever
arbitrary value Python generates. So this is a non-issue.
I think Enums will be good addition to the standard library, and I look
forward to dropping support for Python 3.3 so I can rely on them :-)
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
Re: Python's sad, unimaginative Enum
- Original Message - That's the title of this little beast http://www.acooke.org/cute/Pythonssad0.html if anybody's interested. -- If you're using GoogleCrap™ please read this http://wiki.python.org/moin/GoogleGroupsPython. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list python 2.5 class Enum: class __metaclass__(type): def __iter__(self): for attr in sorted(dir(self)): if not attr.startswith(__): yield getattr(self, attr) class Colours(Enum): RED = red GREEN = green for c in Colours: print c green red JM -- IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you. -- http://mail.python.org/mailman/listinfo/python-list
Re: Python's sad, unimaginative Enum
On Mon, May 13, 2013 at 8:17 PM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: Let's look at his major criticisms: 1) values aren't automatically generated. True. So what? That is the *least* important part of enums. I stopped following the -ideas threads about enums, but IIRC autogeneration of values was in quite a few of the specs early on. So you can probably find the arguments against it in the list archives. FWIW, though, I do like C's autogeneration of enum values - but use it in only a small proportion of my enums. It's not a terrible loss, but it is a loss. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Python's sad, unimaginative Enum
On Mon, 13 May 2013 13:00:36 +0200, Jean-Michel Pichavant wrote: - Original Message - That's the title of this little beast http://www.acooke.org/cute/Pythonssad0.html if anybody's interested. -- If you're using GoogleCrap™ please read this http://wiki.python.org/moin/GoogleGroupsPython. Mark Lawrence -- http://mail.python.org/mailman/listinfo/python-list python 2.5 class Enum: class __metaclass__(type): def __iter__(self): for attr in sorted(dir(self)): if not attr.startswith(__): yield getattr(self, attr) class Colours(Enum): RED = red GREEN = green py class Experience(Enum): ... NOVICE = 'novice' ... GREEN = 'green' ... EXPERIENCED = 'experienced' ... MASTER = 'master' ... py py Colours.GREEN == Experience.GREEN True Oops. It's very easy to make something which does a few things that enums should do, and call it an Enum. It's much harder to do a lot of things that enums should do. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
