Source code for vistir.backports.functools

# -*- coding=utf-8 -*-
from __future__ import absolute_import, unicode_literals

from functools import partial

__all__ = ["partialmethod"]


[docs]class partialmethod(object): """Method descriptor with partial application of the given arguments and keywords. Supports wrapping existing descriptors and handles non-descriptor callables as instance methods. """ def __init__(self, func, *args, **keywords): if not callable(func) and not hasattr(func, "__get__"): raise TypeError("{!r} is not callable or a descriptor".format(func)) # func could be a descriptor like classmethod which isn't callable, # so we can't inherit from partial (it verifies func is callable) if isinstance(func, partialmethod): # flattening is mandatory in order to place cls/self before all # other arguments # it's also more efficient since only one function will be called self.func = func.func self.args = func.args + args self.keywords = func.keywords.copy() self.keywords.update(keywords) else: self.func = func self.args = args self.keywords = keywords def __repr__(self): args = ", ".join(map(repr, self.args)) keywords = ", ".join("{}={!r}".format(k, v) for k, v in self.keywords.items()) format_string = "{module}.{cls}({func}, {args}, {keywords})" return format_string.format( module=self.__class__.__module__, cls=self.__class__.__qualname__, func=self.func, args=args, keywords=keywords, ) def _make_unbound_method(self): def _method(*args, **keywords): call_keywords = self.keywords.copy() call_keywords.update(keywords) if len(args) > 1: cls_or_self, rest = args[0], tuple(args[1:]) else: cls_or_self = args[0] rest = tuple() call_args = (cls_or_self,) + self.args + tuple(rest) return self.func(*call_args, **call_keywords) _method.__isabstractmethod__ = self.__isabstractmethod__ _method._partialmethod = self return _method def __get__(self, obj, cls): get = getattr(self.func, "__get__", None) result = None if get is not None: new_func = get(obj, cls) if new_func is not self.func: # Assume __get__ returning something new indicates the # creation of an appropriate callable result = partial(new_func, *self.args, **self.keywords) try: result.__self__ = new_func.__self__ except AttributeError: pass if result is None: # If the underlying descriptor didn't do anything, treat this # like an instance method result = self._make_unbound_method().__get__(obj, cls) return result @property def __isabstractmethod__(self): return getattr(self.func, "__isabstractmethod__", False)