Source code for nltk.decorators

"""
Decorator module by Michele Simionato <michelesimionato@libero.it>
Copyright Michele Simionato, distributed under the terms of the BSD License (see below).
http://www.phyast.pitt.edu/~micheles/python/documentation.html

Included in NLTK for its support of a nice memoization decorator.
"""

__docformat__ = "restructuredtext en"

## The basic trick is to generate the source code for the decorated function
## with the right signature and to evaluate it.
## Uncomment the statement 'print >> sys.stderr, func_src'  in _decorator
## to understand what is going on.

__all__ = ["decorator", "new_wrapper", "getinfo"]

import sys

# Hack to keep NLTK's "tokenize" module from colliding with the "tokenize" in
# the Python standard library.
OLD_SYS_PATH = sys.path[:]
sys.path = [p for p in sys.path if p and "nltk" not in p]
import inspect

sys.path = OLD_SYS_PATH


def __legacysignature(signature):
    """
    For retrocompatibility reasons, we don't use a standard Signature.
    Instead, we use the string generated by this method.
    Basically, from a Signature we create a string and remove the default values.
    """
    listsignature = str(signature)[1:-1].split(",")
    for counter, param in enumerate(listsignature):
        if param.count("=") > 0:
            listsignature[counter] = param[0 : param.index("=")].strip()
        else:
            listsignature[counter] = param.strip()
    return ", ".join(listsignature)


[docs]def getinfo(func): """ Returns an info dictionary containing: - name (the name of the function : str) - argnames (the names of the arguments : list) - defaults (the values of the default arguments : tuple) - signature (the signature : str) - fullsignature (the full signature : Signature) - doc (the docstring : str) - module (the module name : str) - dict (the function __dict__ : str) >>> def f(self, x=1, y=2, *args, **kw): pass >>> info = getinfo(f) >>> info["name"] 'f' >>> info["argnames"] ['self', 'x', 'y', 'args', 'kw'] >>> info["defaults"] (1, 2) >>> info["signature"] 'self, x, y, *args, **kw' >>> info["fullsignature"] <Signature (self, x=1, y=2, *args, **kw)> """ assert inspect.ismethod(func) or inspect.isfunction(func) argspec = inspect.getfullargspec(func) regargs, varargs, varkwargs = argspec[:3] argnames = list(regargs) if varargs: argnames.append(varargs) if varkwargs: argnames.append(varkwargs) fullsignature = inspect.signature(func) # Convert Signature to str signature = __legacysignature(fullsignature) # pypy compatibility if hasattr(func, "__closure__"): _closure = func.__closure__ _globals = func.__globals__ else: _closure = func.func_closure _globals = func.func_globals return dict( name=func.__name__, argnames=argnames, signature=signature, fullsignature=fullsignature, defaults=func.__defaults__, doc=func.__doc__, module=func.__module__, dict=func.__dict__, globals=_globals, closure=_closure, )
def update_wrapper(wrapper, model, infodict=None): "akin to functools.update_wrapper" infodict = infodict or getinfo(model) wrapper.__name__ = infodict["name"] wrapper.__doc__ = infodict["doc"] wrapper.__module__ = infodict["module"] wrapper.__dict__.update(infodict["dict"]) wrapper.__defaults__ = infodict["defaults"] wrapper.undecorated = model return wrapper
[docs]def new_wrapper(wrapper, model): """ An improvement over functools.update_wrapper. The wrapper is a generic callable object. It works by generating a copy of the wrapper with the right signature and by updating the copy, not the original. Moreovoer, 'model' can be a dictionary with keys 'name', 'doc', 'module', 'dict', 'defaults'. """ if isinstance(model, dict): infodict = model else: # assume model is a function infodict = getinfo(model) assert ( not "_wrapper_" in infodict["argnames"] ), '"_wrapper_" is a reserved argument name!' src = "lambda %(signature)s: _wrapper_(%(signature)s)" % infodict funcopy = eval(src, dict(_wrapper_=wrapper)) return update_wrapper(funcopy, model, infodict)
# helper used in decorator_factory def __call__(self, func): return new_wrapper(lambda *a, **k: self.call(func, *a, **k), func) def decorator_factory(cls): """ Take a class with a ``.caller`` method and return a callable decorator object. It works by adding a suitable __call__ method to the class; it raises a TypeError if the class already has a nontrivial __call__ method. """ attrs = set(dir(cls)) if "__call__" in attrs: raise TypeError( "You cannot decorate a class with a nontrivial " "__call__ method" ) if "call" not in attrs: raise TypeError("You cannot decorate a class without a " ".call method") cls.__call__ = __call__ return cls
[docs]def decorator(caller): """ General purpose decorator factory: takes a caller function as input and returns a decorator with the same attributes. A caller function is any function like this:: def caller(func, *args, **kw): # do something return func(*args, **kw) Here is an example of usage: >>> @decorator ... def chatty(f, *args, **kw): ... print("Calling %r" % f.__name__) ... return f(*args, **kw) >>> chatty.__name__ 'chatty' >>> @chatty ... def f(): pass ... >>> f() Calling 'f' decorator can also take in input a class with a .caller method; in this case it converts the class into a factory of callable decorator objects. See the documentation for an example. """ if inspect.isclass(caller): return decorator_factory(caller) def _decorator(func): # the real meat is here infodict = getinfo(func) argnames = infodict["argnames"] assert not ( "_call_" in argnames or "_func_" in argnames ), "You cannot use _call_ or _func_ as argument names!" src = "lambda %(signature)s: _call_(_func_, %(signature)s)" % infodict # import sys; print >> sys.stderr, src # for debugging purposes dec_func = eval(src, dict(_func_=func, _call_=caller)) return update_wrapper(dec_func, func, infodict) return update_wrapper(_decorator, caller)
def getattr_(obj, name, default_thunk): "Similar to .setdefault in dictionaries." try: return getattr(obj, name) except AttributeError: default = default_thunk() setattr(obj, name, default) return default @decorator def memoize(func, *args): dic = getattr_(func, "memoize_dic", dict) # memoize_dic is created at the first call if args in dic: return dic[args] result = func(*args) dic[args] = result return result ########################## LEGALESE ############################### ## Redistributions of source code must retain the above copyright ## notice, this list of conditions and the following disclaimer. ## Redistributions in bytecode form must reproduce the above copyright ## notice, this list of conditions and the following disclaimer in ## the documentation and/or other materials provided with the ## distribution. ## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ## "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT ## LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR ## A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT ## HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, ## INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, ## BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS ## OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ## ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR ## TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE ## USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH ## DAMAGE.