[Python-ideas] my take on mutable default arguments

[tomer filiba]

i thought this code be solved nicely with a decorator... it needs some
more work, but it would make a good cookbook recipe:

.>>> from copy import deepcopy.
.>>>
.>>> def defaults(**kwdefs):
...     def deco(func):
...         def wrapper(*args, **kwargs):
...             for k,v in kwdefs.iteritems():
...                 if k not in kwargs:
...                     kwargs[k] = deepcopy(v)
...             return func(*args, **kwargs)
...         return wrapper
...     return deco
...
.>>> @defaults(x = [])
... def foo(a, x):
...     x.append(a)
...     print x
...
.>>> foo(5)
[5]
.>>> foo(5)
[5]
.>>> foo(5)
[5]

maybe it should be done by copying func_defaults... then it could
be written as

@copydefaults
def f(a, b = 5, c = []):
    ...


-tomer