"""
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 str(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.