Scope of Functions

Consider the following package design.

package/__init__.py:

import a
import b

package/a.py:

from plum import dispatch


@dispatch
def f(x: int):
   return "int"

package/b.py:

from plum import dispatch


@dispatch
def f(x: float):
   return "float"

In a design like this, the methods for f recorded by dispatch are global:

>>> from package.a import f

>>> f(1.0)
'float'

This could be what you want, but it could also be undesirable. In addition, by using the global @dispatch, someone could accidentally overwrite your methods.

other_package/some_file.py:

from plum import dispatch


# If another package happens to also define `f` for an `int`, then that overwrites
# your method!

@dispatch
def f(x: int):
    ...

To prevent this from happening and to keep your functions private, you can create new dispatchers.

package/__init__.py:

import a
import b

package/a.py:

from plum import Dispatcher

dispatch = Dispatcher()


@dispatch
def f(x: int):
   return "int"

package/b.py:

from plum import Dispatcher

dispatch = Dispatcher()


@dispatch
def f(x: float):
   return "float"

>>> from package.a import f

>>> f(1)
'int'

>>> f(1.0)
NotFoundLookupError: For function `f`, `(1.0,)` could not be resolved.

>>> from package.b import f

>>> f(1)
NotFoundLookupError: For function `f`, `(1,)` could not be resolved.

>>> f(1.0)
'float'