Is it possible to change the return value of a function without defining a new function in python?

Question

def foo(a, b, c = 0):
    return a+b

I have dozens of functions like "foo" that have different argument numbers and names. Is there a general way to get the return values ​​of these functions and perform only one additional operation, such as pformat?

Yes, I can just generate a new function, such as:

func = ...  # func can be got using getattr by name
def wrapper(*arg, **kw):
    data = func(*arg, **kw)
    return pprint.pformat(data)
return wrapper

But then the new "wrapper" function is different from the old "func", for example, in the argument number, "wrapper" has only 2 arguments - "arg" and "kw", but "func" can have many arguments, such as 'a' , 'b', 'c'.

I just want to play with the return value, everything else should remain in place, is this possible?

Thank!

, decorator :

--- /home/jaime/cache/decorator-3.2.0/src/decorator.py  2010-05-22 23:53:46.000000000 +0800
+++ decorator.py    2010-10-28 14:55:11.511140589 +0800
@@ -66,9 +66,12 @@
             self.name = '_lambda_' 
             self.doc = func.__doc__
             self.module = func.__module__
-            if inspect.isfunction(func):
+            if inspect.isfunction(func) or inspect.ismethod(func):
                 argspec = inspect.getargspec(func)
                 self.args, self.varargs, self.keywords, self.defaults = argspec
+                if inspect.ismethod(func):
+                    self.args = self.args[1:] # Remove the useless 'self' arg
+                    argspec = inspect.ArgSpec(self.args, self.varargs, self.keywords, self.defaults)
                 for i, arg in enumerate(self.args):
                     setattr(self, 'arg%d' % i, arg)
                 self.signature = inspect.formatargspec(

, "", decorator.decorator , .

:

def __getattr__(self, attr):
    def pformat_wrapper(f, *args, **kw):
        data = f(*args, **kw)
        return pprint.pformat(data, indent = 4)

    method = getattr(self.ncapi, attr)
    return decorator(pformat_wrapper, method) # Signature preserving decorating





jaime@westeros:~/bay/dragon.testing/tests$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56) 
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import decorator
>>> class A:
...   def f(self):
...       pass
... 
>>> a = A()
>>> a.f
<bound method A.f of <__main__.A instance at 0xb774a20c>>
>>> def hello(f, *args, **kw):
...     print 'hello'
...     return f(*args, **kw)
... 
>>> f1 = decorator.decorator(hello, a.f)
>>> f1()
hello
>>>

Answer 1

:

" " " " func ", , → ," wrapper " 2 -" arg "" kw ", func ' → args, ' a ',' b ',' c '."

decorator, , .

Answer 2

.

from functools import wraps
def pformat_this( someFunc ):
    @wraps( someFunc )
    def wrapper(*arg, **kw):
        data = someFunc(*arg, **kw)
        return pprint.pformat(data)
    return wrapper


@pformat_this
def foo(a, b, c = 0):
    return a+b

Answer 3

, .

, python 2.7 , , Callable types → . , .

, , , , → . , promises API, , .

, -, , . , - .