Enumerations

Enumerations are a way to define a type that can only have a certain set of values. This is useful when you want to restrict a variable to only be able to have a certain set of values.

Enumerations are created using the Enum class from the enum module.

from enum import Enum


class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3


print(Color.RED)
# > Color.RED

print(Color.RED.name)
# > RED

print(Color.RED.value)
# > 1

auto()

The auto() function can be used to automatically assign values to the enumeration members. This is preferable to manually assigning values because it prevents the values from being accidentally duplicated.

from enum import Enum, auto


class Color(Enum):
    RED = auto()
    GREEN = auto()
    BLUE = auto()


print(Color.RED)
# > Color.RED

print(Color.RED.name)
# > RED

print(Color.RED.value)
# > 1

Iterating Over Enumerations

You can iterate over the values of an enumeration by iterating over the enumeration class itself.

from enum import Enum


class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3


for color in Color:
    print(color)
# > Color.RED
# > Color.GREEN
# > Color.BLUE

Flags

Flags are enumerations that can be combined using the bitwise operators | (or), & (and), ^ (xor), ~ (not).

from enum import Flag, auto

class Color(Flag):
    RED = auto()
    GREEN = auto()
    BLUE = auto()

print(Color.RED)
# > Color.RED

print(Color.RED.name)
# > RED

print(Color.RED.value)
# > 1

print(Color.RED | Color.GREEN)
# > Color.RED|GREEN

print(Color.RED | Color.GREEN | Color.BLUE)
# > Color.RED|GREEN|BLUE

Flag Operations

There are multiple operations that can be performed on flags. These include:

• | (or) - combines the flags
• & (and) - returns the flags that are common to both flags
• ^ (xor) - returns the flags that are not common to both flags
• ~ (not) - returns the flags that are not in the flag
• == (equals) - returns true if the flags are equal
• != (not equals) - returns true if the flags are not equal
• in - returns true if the flag is in the flag
• not in - returns true if the flag is not in the flag

from enum import Flag, auto

class Color(Flag):
    RED = auto()
    GREEN = auto()
    BLUE = auto()

print(Color.RED | Color.GREEN)
# > Color.RED|GREEN

print(Color.RED & Color.GREEN)
# > 0

print(Color.RED ^ Color.GREEN)
# > Color.RED|GREEN

print(~Color.RED)
# > Color.GREEN|BLUE

print(Color.RED == Color.RED)
# > True

print(Color.RED == Color.GREEN)
# > False

print(Color.RED != Color.RED)
# > False

print(Color.RED != Color.GREEN)
# > True

print(Color.RED in Color.RED)
# > True

print(Color.RED in Color.GREEN)
# > False

print(Color.RED not in Color.RED)
# > False

print(Color.RED not in Color.GREEN)
# > True

print(Color.RED in Color.RED | Color.GREEN)
# > True

print(Color.RED in Color.GREEN | Color.BLUE)
# > False