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# Copyright (C) 2007 Dan Pascu. See LICENSE for details.
#
"""Helper functions for writing well behaved decorators."""
__all__ = ['decorator', 'preserve_signature']
def decorator(func):
"""A syntactic marker with no other effect than improving readability."""
return func
def preserve_signature(func):
"""Preserve the original function signature and attributes in decorator wrappers."""
from inspect import getargspec, formatargspec
signature = formatargspec(*getargspec(func))[1:-1]
parameters = formatargspec(*getargspec(func), **{'formatvalue': lambda value: ""})[1:-1]
def fix_signature(wrapper):
code = "def %s(%s): return wrapper(%s)\nnew_wrapper = %s\n" % (func.__name__, signature, parameters, func.__name__)
exec code in locals(), locals()
#expression = "lambda %s: wrapper(%s)" % (signature, parameters)
#new_wrapper = eval(expression, {'wrapper': wrapper})
new_wrapper.__name__ = func.__name__
new_wrapper.__doc__ = func.__doc__
new_wrapper.__module__ = func.__module__
new_wrapper.__dict__.update(func.__dict__)
return new_wrapper
return fix_signature
__usage__ = """
from application.python.decorator import decorator, preserve_signature
# indicate that the next function will be used as a decorator (optional)
@decorator
def print_args(func):
@preserve_signature(func)
def wrapper(*args, **kwargs):
print "arguments:", args, kwargs
return func(*args, **kwargs)
return wrapper
@print_args
def foo(x, y, z=7):
return x + 3*y + z*z
"""
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