Anomaly in creating class methods
Hi, given below is my interaction with the interpreter In one case, i have created the class method using the "famous idiom"... and in the other, i have tried to create it outside the class definition... why isn't the latter working ? (of course, the presence of decorators is a different issue) >>> class D: ... def f(cls): ... print cls ... >>> D.f=classmethod(D.f) >>> D.f > >>> D.f() Traceback (most recent call last): File "", line 1, in ? TypeError: unbound method f() must be called with D instance as first argument (got classobj instance instead) >>> class D: ... def f(cls): ... print cls ... f=classmethod(f) ... >>> D.f > >>> D.f() __main__.D -- http://mail.python.org/mailman/listinfo/python-list
Re: Class Variable Access and Assignment
You see, The seen behavior is due to the result of python's name binding,scoping scheme. Let me give you an example, class A: i=0 def t(self): print self.i self.i=4 then a=A() a.i is 0 a.t() then, A.i is 0 a.i is 4 In the function, it first searches for i in its local scope, on not finding it, accesses the class object's i. then the next line, is an assignment, which binds (creates a new variable) in the instance's scope. you can use the buit-in id function to verify it. the same thing happens in the case of b.a = b.a + 2 search for b.a not found, read the value from the enclosing scope (of the class object) then assign b.a to the local scope, with the value 3. But, I think your question about the sanity of the behaviour should be analysed sincerely if, k=0 def f(): print k k=k+1 raises UnboundLocalError, then how is it accepted in the former case? hmmm maybe, my arguments are hapazard but, i'll get to know when i'm flamed ;) -- http://mail.python.org/mailman/listinfo/python-list
Re: OT - Re: Microsoft Hatred FAQ
Hi, Though out of the streamline, I find your post to be one of the most reasonable and well-formed arguments I have read in a long time. Keep it up. Great work. Steven D'Aprano wrote: Real standards, like TCP/IP which is the backbone of the Internet, aren't controlled by any one company. Anyone can create a TCP stack. Nobody but Microsoft can create a competing version of Windows. TCP/IP became a standard long before Microsoft even acknowledged it's existence. So did ASCII, the IBM BIOS, and serial ports, to name just a few. Does the term "ISO standard" mean anything to you? -- http://mail.python.org/mailman/listinfo/python-list
Re: Class Variable Access and Assignment
hey, did u read my reply fully? i too feel that this matter of raising unbound local error in one case and not raising it in the other must be analysed... quoting from the documentation "If a name binding operation occurs anywhere within a code block, all uses of the name within the block are treated as references to the current block. This can lead to errors when a name is used within a block before it is bound. This rule is subtle. Python lacks declarations and allows name binding operations to occur anywhere within a code block. The local variables of a code block can be determined by scanning the entire text of the block for name binding operations." -- http://mail.python.org/mailman/listinfo/python-list
Re: Class Variable Access and Assignment
Again (blink) quoting from the docs " For targets which are attribute references, the initial value is retrieved with a getattr() and the result is assigned with a setattr(). Notice that the two methods do not necessarily refer to the same variable. When getattr() refers to a class variable, setattr() still writes to an instance variable. For example: class A: x = 3# class variable a = A() a.x += 1 # writes a.x as 4 leaving A.x as 3 " I felt a wee bit clear after going thru the doc... attribute referencing is not the same as searching the variable in the enclosing scopes But, i still feel the inconsistency... -- http://mail.python.org/mailman/listinfo/python-list
Re: Anomaly in creating class methods
Cool, i got it now... accessing thru attribute reference always returns a bound or unbound method... so, D.f is an unbound method whereas i want the "function" of the unbound method... ok, this example and the nice explanations definitively thought me about function, bound method (for which the function is just an attribute accessed by im_func) and unbound method... Also, calling classmethod on an unbound method instead of a function is a strict no... no... ok... nice concept... But, i am at loss when i come to clearly understanding the difference between new-style classes and classic classes (or should i post it as new topic?). -- http://mail.python.org/mailman/listinfo/python-list
Re: reading internet data to generate random numbers.
hotbits hotbits hotbits! http://www.fourmilab.ch/hotbits/ based on quantum mechanics check it out! -- http://mail.python.org/mailman/listinfo/python-list
Diff. between Class types and classic classes
Hi, can some one properly explain the differences between class types and classic classes? ... Still face problems in identifying what is what. -- http://mail.python.org/mailman/listinfo/python-list
Re: Diff. between Class types and classic classes
Dear Colin, Forgive me for this late reply. Your explanation was of great help to me. Thank you very much. It was crystal clear. -- http://mail.python.org/mailman/listinfo/python-list
Changing fill in tkinter
Hi, I would like to know how to change the fill of things we put in a tkinter's canvas. for example, if i create a rectangle and i would want to change the fill of the rectangle once it is clicked... can we do that? -- http://mail.python.org/mailman/listinfo/python-list
Re: Changing fill in tkinter
yes, it was a stupid mistake from my part in not pondering over the api fully. forgive me. anyways, ii was just looking for item configure. (I was spending all my time searching google rather than reading the api sincerely. duh...) -- http://mail.python.org/mailman/listinfo/python-list
