Created
October 25, 2018 08:14
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Python overloading annotation
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#-*-coding: utf-8;-*- | |
""" | |
Overloaded function for python | |
""" | |
from sys import _getframe as gf | |
from inspect import signature as sig, _ParameterKind as kind, _empty as empty | |
class _function: | |
def __init__(self, func): | |
self.fn = func | |
self.sig = sig(func) | |
self._signature = tuple( | |
(a.annotation, a.kind) if isinstance(a.annotation, type) else None | |
for a in self.sig.parameters.values()) | |
def match(self, *args, **kwargs): | |
try: | |
bound = self.sig.bind(*args, **kwargs) | |
except TypeError: | |
return 0 | |
priority = 1 | |
for key, arg in bound.arguments.items(): | |
param = self.sig.parameters[key] | |
if not isinstance(param.annotation, type) or param.annotation is empty: | |
continue | |
if not isinstance(arg, param.annotation): | |
return 0 | |
priority += 1 | |
return priority | |
def __eq__(self, other): | |
if not isinstance(other, type(self)): | |
raise NotImplementedError | |
return self._signature == other._signature | |
def __ne__(self, other): | |
if not isinstance(other, type(self)): | |
raise NotImplementedError | |
return self._signature != other._signature | |
def __call__(self, *args, **kwargs): | |
return self.fn(*args, **kwargs) | |
class _dispatcher: | |
def __init__(self): | |
self.__funcs = [] | |
def append(self, fn): | |
fnc = _function(fn) | |
for f in self.__funcs: | |
if fnc == f: | |
raise TypeError(f"A function with signature {f.sig} is alredy defined.") | |
self.__funcs.append(fnc) | |
def __call__(self, *args, **kwargs): | |
guess = [] | |
for f in self.__funcs: | |
p = f.match(*args, **kwargs) | |
if p == 0: | |
continue | |
guess.append((p, f)) | |
if not guess: | |
raise TypeError("No function was matched to the argument.") | |
guess.sort(key=lambda x: x[0]) | |
return guess[-1][1](*args, **kwargs) | |
def overload(fn): | |
name = fn.__name__ | |
frame = gf(1) | |
if name not in frame.f_locals: | |
ol = _dispatcher() | |
else: | |
ol = frame.f_locals[name] | |
ol.append(fn) | |
return ol |
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