[Python-Dev] PEP 435 -- Adding an Enum type to the Python standard library (original) (raw)

Serhiy Storchaka storchaka at gmail.com
Fri Apr 26 18:27:18 CEST 2013

26.04.13 18:50, Larry Hastings написав(ла):

On 04/26/2013 12:34 AM, Greg Ewing wrote:

Or if, as Guido says, the only sensible things to use as enum values are ints and strings, just leave anything alone that isn't one of those. The standard Java documentation on enums: http://docs.oracle.com/javase/tutorial/java/javaOO/enum.html has an example enum of a "Planet", a small record type containing mass and radius--each of which are floats. I don't know whether or not it constitutes good programming, but I'd be crestfallen if Java enums were more expressive than Python enums ;-)

This example requires more than features discussed here. It requires an enum constructor.

class Planet(Enum): MERCURY = Planet(3.303e+23, 2.4397e6) VENUS = Planet(4.869e+24, 6.0518e6) EARTH = Planet(5.976e+24, 6.37814e6) MARS = Planet(6.421e+23, 3.3972e6) JUPITER = Planet(1.9e+27, 7.1492e7) SATURN = Planet(5.688e+26, 6.0268e7) URANUS = Planet(8.686e+25, 2.5559e7) NEPTUNE = Planet(1.024e+26, 2.4746e7)

 def __init__(self, mass, radius):
     self.mass = mass     # in kilograms
     self.radius = radius # in meters

 @property
 def surfaceGravity(self):
     # universal gravitational constant  (m3 kg-1 s-2)
     G = 6.67300E-11
     return G * self.mass / (self.radius * self.radius)

 def surfaceWeight(self, otherMass):
     return otherMass * self.surfaceGravity

This can't work because the name Planet in the class definition is not defined.

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