Plum: Multiple Dispatch in Python
Everybody likes multiple dispatch, just like everybody likes plums.
Installation
Plum requires Python 3.7 or higher.
pip install plum-dispatchDocumentation
See here.
What's This?
Plum brings your type annotations to life:
from numbers import Number
from plum import dispatch
@dispatch
def f(x: str):
return "This is a string!"
@dispatch
def f(x: int):
return "This is an integer!"
@dispatch
def f(x: Number):
return "This is a general number, but I don't know which type.">>> f("1")
'This is a string!'
>>> f(1)
'This is an integer!'
>>> f(1.0)
"This is a number, but I don't know which type."
>>> f(object())
NotFoundLookupError: For function "f", signature Signature(builtins.object) could not be resolved.This also works for multiple arguments, enabling some neat design patterns:
from numbers import Number, Real, Rational
from plum import dispatch
@dispatch
def multiply(x: Number, y: Number):
return "fallback implementation of multiplication"
@dispatch
def multiply(x: Real, y: Real):
return "specialised implementation for reals"
@dispatch
def multiply(x: Rational, y: Rational):
return "specialised implementation for rationals">>> multiply(1, 1)
'specialised implementation for rationals'
>>> multiply(1.0, 1.0)
'specialised implementation for reals'
>>> multiply(1j, 1j)
'fallback implementation of multiplication'
>>> multiply(1, 1.0) # For mixed types, it automatically chooses the right optimisation!
'specialised implementation for reals'