Simple overloading of methods and functions through an @overload decorator.
This module allows one to provide multiple interfaces for a functions,
methods, classmethods, staticmethods or classes. See below for some notes
about overloading classes, you strange person you.
The appropriate implementation is chosen based on the calling argument
pattern.
For example:
class A(object):
... @overload
... def method(self, a):
... return 'a'
... @method.add
... def method(self, a, b):
... return 'a, b'
...
a = A()
a.method(1)
'a'
a.method(1, 2)
'a, b'
The overloading handles fixed, keyword, variable (*args
) and arbitrary
keyword (**keywords
) arguments.
It also handles annotations if those annotations are types:
@overload
... def func(a:int):
... return 'int'
...
@func.add
... def func(a:str):
... return 'str'
...
func(1)
'int'
func('s')
'str'
func(1.0)
Traceback (most recent call last):
File "", line 1, in
File "overload.py", line 94, in f
raise TypeError('invalid call argument(s)')
TypeError: invalid call argument(s)
This feature (and currently the module in general) requires Python 3.
The docstring and name (ie. documentation) of the resultant callable will
match that of the first callable overloaded.
Overloading Classes
Overloading classes allows you to select a class type based on the
construction arguments of each alternative type's new method.
There's a catch though: the new method must explicitly invoke the
base class new method, rather than use super() like usual. This is
because after being @overloaded the class is a function, and super()
doesn't like being passed functions. So instead of::
@overload
class A(object):
def __new__(cls):
# this will fail because "A" is a function now
return super(A, cls).__new__(cls)
you must::
@overload
class A(object):
def __new__(cls):
# must explicitly reference the base class
return object.__new__(cls)
I'll leave it up to the reader to justify their use of @overloading
classes.
Version History (in Brief)
- 1.1 altered the text of the invalid call TypeError. Removed debug prints.
- 1.0 the initial release
See the end of the source file for the license of use.
I would be interested to know whether this module is useful - if you use it
please indicate so at https://www.ohloh.net/p/pyoverload