enumatch

Strictly match all the possibilities of an enum.

Use case

This little match function makes matching Python's enum fields safer by forcing us to match all the possibilities either explicitly or by using a wildcard.

Use ... (ellipsis) for the wildcard.

TIPs

• Avoid the use of ... (wildcard) to make sure any modification to the enums are safe.
• Create the matcher at compile-time to have compile-time validation and zero runtime cost.

Example: Flat matcher

from enum import Enum, auto
from enumatch import match

class Side(Enum):
    left = auto()
    right = auto()

# Define a simple matcher
matcher1 = match({Side.left: "Go left", Side.right: "Go right"})

assert matcher1[Side.left] == "Go left"
assert matcher1[Side.right] == "Go right"

# Define a matcher with a default case
matcher2 = match({Side.left: "Go left", ...: "Go right"})

assert matcher2[Side.left] == "Go left"
assert matcher2[Side.right] == "Go right"

# If all the possibilities are not handled, we get error
with pytest.raises(ValueError, match="missing possibilities: Side.right"):
    match({Side.left: "Go left"})

Example: Nested matcher

from enum import Enum, auto
from enumatch import match, forall

class Switch(Enum):
    on = auto()
    off = auto()

# is_on[main_switch][bedroom_switch]: bool
is_on = match({
    Switch.on: match({Switch.on: True, Switch.off: False}),
    Switch.off: forall(Switch, False),
})

assert is_on[Switch.on][Switch.on] == True
assert is_on[Switch.on][Switch.off] == False
assert is_on[Switch.off][Switch.on] == False
assert is_on[Switch.off][Switch.off] == False