enum in Python

[Andrew Chalk]

What is the best way to implement an equivalent of C's 'enum' type in
Python?

As a rank Python beginner I've used a dictionary, but presumably there is a
better way.

Thanks

 

[David M. Cook]

As a rank Python beginner I've used a dictionary, but presumably there is a
better way.

I've seen idioms like

FOO, BAR, BAZ = range(3)

used.

Dave Cook

 

[Sean Ross]

What is the best way to implement an equivalent of C's 'enum' type in
Python?

As a rank Python beginner I've used a dictionary, but presumably there is a
better way.

Thanks

Hi.

This c.l.py thread may be helpful:
http://mail.python.org/pipermail/python-list/2003-February/149342.html

as may this cookbook recipe:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/67107

 

[Scott David Daniels]

I've seen idioms like

FOO, BAR, BAZ = range(3)

used.

Dave Cook

For 2.3 or after:

class Enumerate(object):
def __init__(self, names):
for number, name in enumerate(names.split()):
setattr(self, name, number)

To use:
codes = Enumerate('FOO BAR BAZ')
codes.BAZ will be 2 and so on.


if you only have 2.2, precede this with:

from __future__ import generators

def enumerate(iterable):
number = 0
for name in iterable:
yield number, name
number += 1




codes.BAZ

 

[Harry George]

For 2.3 or after:

class Enumerate(object):
def __init__(self, names):
for number, name in enumerate(names.split()):
setattr(self, name, number)

To use:
codes = Enumerate('FOO BAR BAZ')
codes.BAZ will be 2 and so on.


if you only have 2.2, precede this with:

from __future__ import generators

def enumerate(iterable):
number = 0
for name in iterable:
yield number, name
number += 1




codes.BAZ

We have some code which uses fancy cookbooked enumerate patterns but
they seem unnecessarily complex to me. Even the pattern above is a
runtime build of what should be a static type definition. Instead, in
any Python version, I use:

class Code:
unknown=0
FOO=1
BAR=2
BAZ=3

mycode=Code.unknown #typical initialization

mycode=Code.FOO #specific value assigned.

You get:
a) type-specific namespace

b) can choose the numbers (e.g., when they are predefined in a data
file format)

c) errors are detected

d) static assignment allows compiler optimizations (don't know if
any are actually done).