Python C Extension Decoder

Question

I apologize in advance for the long background information.

I recently met with the Python / C-API (Python 3.4) and got a dead end. My goal is to have a C extension that I can use as a function / method decorator. I have a fairly experienced prototype for the LRU cache in gist, https://gist.github.com/pbrady/916495198910e7d7c713 . Although the cache works and works very fast, there are two problems:

• typereturned by my decorator does not work: ie

  >>> from lrucache import lrucache
  >>> @lrucache()
  ... def f(a, b):
  ...    return a+b
  ...
  >>> type(f)
  >>> <class 'lrucache.cache'>
  

  Because of this, the decorator does not work properly on methods - it seems to be selflost because Python does not create an instance method when it sees my class (which makes sense).

• Copying __doc__from a decorated function to my cache class does not affect the message displayed help.

My idea to get around these problems was to simply return a user-defined function with several modifications, rather than with a new user-defined class. These changes

• Add an attribute __wrapped__to the function and specify its function.

• Overwrite attribute __call__so that function calls are routed to user C routine.

I was able to fulfill (1), but redefining the functions of the __call__method does nothing, since it is usually not used by the interpreter.

My question is (finally): How to create a Python function (i.e. PyFunctionObject) that will call the C function?

, , . / , Cython.

Answer 1

(2), , , , :

In [1]: class Test:
   ...:     def __call__(self):
   ...:         print('Called class attribute!')
   ...:         

In [2]: t = Test()

In [3]: def new_call():
   ...:     print('Called instance attribute!')
   ...:     

In [4]: t.__call__ = new_call

In [5]: t()
Called class attribute!

function class __call__, python.

, PyFunctionObject, PyFunction_New. , PyCodeObject , :

• PyCode_NewEmpty: . , .
• PyCode_New: -. 14 , - PyObject *code, , -.
• Py_CompileStringObject: . compile.

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:

• lrucache a descriptor. , python , self , .

• python, C ​​, :

  from functools import wraps
  
  from _lrucache import cache
  
  def lrucache(func):
      cached_func = cache(func)
  
      @wraps(func)
      def wrapper(*args, **kwargs):
          return cached_func(*args, **kwargs)
  
      return wrapper
  

  , python.

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