enum since Python 3.4 and Java 1.5

Using enum in both languages is usually preferred than a group of named int constants.

Python 3.4 adds the enum module that provides very similar feature set with Java enum type added in Java 1.5. Python’s enum makes heavy use of metaclass machinery whereas Java’s enum is more or less syntactic sugar. They both offer you:

• Defining classes with a finite set of members.
• Referring to members by name (and Python allows you to refer to members by value as well).
• Iterating over members.
• Members are unique and can be compared by identity.
• Members are unordered.
• You are disallowed to compare members with integers.

Java enum cannot be extended because every enum type implicitly extends java.lang.Enum and Java dose not support multiple inheritance.

// This is illegal.
enum MyEnumType extends Whatever { ... }

In Python, you may add members to a sub-enum if the parent does not define any members:

class Color(Enum):
    red = 10
    green = 11
    blue = 12

# TypeError: Cannot extend enumerations
class MoreColor(Color):
    black = 0
    white = 1

It is sometimes a very useful trick to extend a enum:

# This is how enum module implements IntEnum.
class IntEnum(int, Enum):
    pass