C[omp]ute

From: andrew cooke <andrew@...>

Date: Sat, 11 May 2013 11:03:33 -0400

Python is about to get an Enum.  See http://www.python.org/dev/peps/pep-0435/

And it's sad.

It's not awful.  It just fails to do anything particularly well - it's an
awkward compromise whose only real achievement is not doing anything new.

What would you expect a Pythonic enum to look like?

  class Colour(Enum):
      red
      green

  > print(Colour.red == Colour.green)
  false

That's about the minimum, right?  But it doesn't do that.  The above would
require new syntax, so instead you have to define values:

  class Colour(Enum):
      red = 1
      green = 1

Still, at least the mistake above would raise an error.  Wouldn't it?  Nope.
That's a feature.  If you mess up on the non-optional values then you get
"aliases".  Because that's something I've waited all my life for, while I
never make mistakes...  Or something.  The something being that they are
smoking fucking crack.

But you could just as well type:

  class Colour:
      red = 1
      green = 2

so what does Enum get you?  It provides a bit of metaclass goop to let you
iterate over values, etc.  Whoop.

So, you go hunting around in the docs to see if there's any way at all of
avoiding the need to assign values manually.  And there is:

  Colour = Enum('Colour', 'red, green')

which suffers from the same problems as namedtuples:
  - 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).

Now if two potentially useful library classes are suffering from the same
problems than isn't that a BIT OF A HINT to try make things better?  Nope.  It
just shows how important it is to not be imaginative.  Or something (crack).

And it gets worse.  What values do you think the above provides?

Strings?  That would makes sense (red = 'red'), in that it would display
nicely and is going to provide easy to debug values.  So nope.

Integers from zero?  I mean that's how Python counts indices and there's "only
one way to do it" so that's how Python counts enums, right?  Nope.

OK, so bit fields?  That way we can do cool Colour.red | Colour.green and
make the C programmers feel at home?  Nope.

Give up?  I'll tell you.  It counts from 1.  Presumably because it's really
common to use the "if not enum" idiom.  In someone's crack-addled dreams.


Like I said at the start.  None of this is really awful.  It's just lame.
It's design by committee that finds the least offensive, least imaginative,
least useful solution.

One big pile of meh.

Andrew