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"""
Decorator module, see
http://www.phyast.pitt.edu/~micheles/python/documentation.html
for the documentation and below for the licence.
"""
## 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 inspect, sys
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)
- 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'
"""
assert inspect.ismethod(func) or inspect.isfunction(func)
regargs, varargs, varkwargs, defaults = inspect.getargspec(func)
argnames = list(regargs)
if varargs:
argnames.append(varargs)
if varkwargs:
argnames.append(varkwargs)
signature = inspect.formatargspec(regargs, varargs, varkwargs, defaults,
formatvalue=lambda value: "")[1:-1]
return dict(name=func.__name__, argnames=argnames, signature=signature,
defaults = func.func_defaults, doc=func.__doc__,
module=func.__module__, dict=func.__dict__,
globals=func.func_globals, closure=func.func_closure)
# akin to functools.update_wrapper
def update_wrapper(wrapper, model, infodict=None):
infodict = infodict or getinfo(model)
try:
wrapper.__name__ = infodict['name']
except: # Python version < 2.4
pass
wrapper.__doc__ = infodict['doc']
wrapper.__module__ = infodict['module']
wrapper.__dict__.update(infodict['dict'])
wrapper.func_defaults = infodict['defaults']
return wrapper
def new_wrapper(wrapper, model):
"""
An improvement over functools.update_wrapper. It generates a copy of the
wrapper with the right signature and updates 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
return update_wrapper(eval(src, dict(_wrapper_=wrapper)), model, infodict)
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'
"""
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)
if __name__ == "__main__":
import doctest; doctest.testmod()
####################### 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.
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