Re: Accessing func_name from inside a function
Scott David Daniels wrote: > Eyal Lotem wrote: >> By the way, the "real" problem here is referencing by name, rather than >> using "true" references. Which is the result of using a textual language. >> The "real" solution would be to store real-references to the function and >> only present the name in a graphical interface. > > There is a problem with this attitude (to which I used to subscribe). > Just as what constitutes a mathematical proof is a social agreement > among mathematicians, programmers need to be able to read programs > by other programmers. People do not communicate in data structures. > I worked with LML, a lazy ML variant that (among other things) allowed > specification of the print form of structures. I wound up debugging > (for a nasty 12 hours) a program which printed identically to the > correct program, but was not, in fact, the correct program. That one > experience has convinced me that programs are defined in print, not > structures. Well, what you describe is a hidden semantic difference, which is a problem of the view, not of the representation. As long as the view can display the details of the program in their entirety, text has no advantage in this aspect. There is no reason why replacing the textual backend with a richer object model and true references would prevent a simple viewer that renders the programs as simple text similar to the way they look today. It would seem almost equivalent but suddenly easy renames, diff tracking for source control, and semantic editing would not only be possible but easy. -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
Eyal Lotem wrote: > By the way, the "real" problem here is referencing by name, rather than > using "true" references. Which is the result of using a textual language. > The "real" solution would be to store real-references to the function and > only present the name in a graphical interface. There is a problem with this attitude (to which I used to subscribe). Just as what constitutes a mathematical proof is a social agreement among mathematicians, programmers need to be able to read programs by other programmers. People do not communicate in data structures. I worked with LML, a lazy ML variant that (among other things) allowed specification of the print form of structures. I wound up debugging (for a nasty 12 hours) a program which printed identically to the correct program, but was not, in fact, the correct program. That one experience has convinced me that programs are defined in print, not structures. --Scott David Daniels [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
Alex Martelli wrote: > Ron Adam <[EMAIL PROTECTED]> wrote: > >> A "Current" key word would fix this. Or possibly "This" which would be >> short for "This object". > > I think "This" would cause huge confusion, since in other popular > language the keyword "this" means (a pointer/reference to) "the instance > variable on which the method is being called" -- my use is instead for > "the object of the immediate lexically enclosing scope" (a module, > class, or function). Implementation wouldn't be trivial in today's > CPython, anyway: frames have no references at all to function objects > (only to _code_ objects), and class objects don't even exist untill well > after their top-level code has long finished running; to make Current > possible, these subtle points of semantics would have to be changed in > quite a revolutionary way, especially where classes are concerned. > > > Alex Yes, I figured it would not be an easy or simple addition. An easier alternative might be to be able to limit specific name rebindings. Then some names could be depended on to always point to a specific object. Something like that would need to be used sparingly I think. Cheers, Ron -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
Steven D'Aprano wrote: > On Sun, 26 Mar 2006 10:19:36 +1000, Ben Finney wrote: > >> "James Thiele" <[EMAIL PROTECTED]> writes: >> >>> I'd like to access the name of a function from inside the function. >> >> A function, like most other objects in Python, can have any number of >> names bound to it without the object being informed. Any of those >> names can then be used to reference the object, and the object has no >> way of knowing by what name it was referenced. >> >> Because of this fallacy, > > "You keep using that word. I do not think it means what you think it > means." > > *wink* > >> it's generally considered bad programming >> style to want to know "the" name of the current object from inside >> that object. > > I agree whole-heartedly with Ben's sentiments here, although I can also > point out by example why it might be useful for a function to know it's > own name: > > def Ackermann(i, j): > """Returns the Ackermann function of integers i and j. > > The Ackermann function is an example of a function which grows at a > much faster than exponential rate. Ackermann(i, j) for i > 2 grows > even more quickly than 2**2**2**...**2 (where there are j exponents). > It is an example of a recursive function which is not primitively > recursive and was discovered by the German mathematician Wilhelm > Ackermann in 1928. > > >>> Ackermann(1, 1) > 2 > >>> Ackermann(2, 2) > 16 > >>> Ackermann(2, 3) > 65536 > > The Ackermann function is not defined for i,j <= 0. > > See http://en.wikipedia.org/wiki/Ackermann_function > and 'Introduction to Algorithms' by Thomas H Cormen, Charles E > Leiserson, Ronald L Rivest, pp. 451-453. > """ > if i < 0 or j < 0: > raise ValueError( > "arguments to the Ackermann function must be positive") > if i == 1: > return 2**j > if j == 1: > return Ackermann(i-1, 2) > return Ackermann(i-1, Ackermann(i, j-1)) > > Notice that if you change the name of the function, you have to change it > in no less than three places in the function definition and four places > in the __doc__ string, but a global search and replace is too greedy and > will change too much. As a general principle, it is considered best > practice to code in such a way that if you change something, you only need > to change it in one place. > > I guess that the Original Poster wants some magic that allows functions to > do this: > > def Ackermann(i, j): > """Returns the Ackermann function of integers i and j. > > The Ackermann function is an example of a function which grows at a > much faster than exponential rate. %MAGIC(i, j) for i > 2 grows > even more quickly than 2**2**2**...**2 (where there are j exponents). > It is an example of a recursive function which is not primitively > recursive and was discovered by the German mathematician Wilhelm > Ackermann in 1928. > > >>> %MAGIC(1, 1) > 2 > >>> %MAGIC(2, 2) > 16 > >>> %MAGIC(2, 3) > 65536 > > The Ackermann function is not defined for i,j <= 0. > > See http://en.wikipedia.org/wiki/Ackermann_function > and 'Introduction to Algorithms' by Thomas H Cormen, Charles E > Leiserson, Ronald L Rivest, pp. 451-453. > """ > if i < 0 or j < 0: > raise ValueError( > "arguments to the Ackermann function must be positive") > if i == 1: > return 2**j > if j == 1: > return %MAGIC(i-1, 2) > return %MAGIC(i-1, %MAGIC(i, j-1)) Another possibility would be: def recursive_func(func): def new_func(*args, **kw): return func(new_func, *args, **kw) return new_func @recursive_func def Ackermann(recurse, i, j): # yadda yadda recurse(i-1, ...), recurse(y-2, ...) > Now he can easily rename "Ackermann" to "Ack" and need only make the > change in one place. > > I suspect that the correct solution to the O.P.'s problem is to think > carefully about the names of your functions in advance. By the way, the "real" problem here is referencing by name, rather than using "true" references. Which is the result of using a textual language. The "real" solution would be to store real-references to the function and only present the name in a graphical interface. -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
James Thiele <[EMAIL PROTECTED]> wrote: > I'd like to access the name of a function from inside the function. My > first idea didn't work. > > >>> def foo(): > ... print func_name > ... > >>> foo() > Traceback (most recent call last): > File "", line 1, in ? > File "", line 2, in foo > NameError: global name 'func_name' is not defined So, define it -- as a function, of course: def func_name(): import sys return sys._getframe(1).f_code.co_name def foo(): print func_name() def bar(): print func_name() No doubt you'll object that the internals of func_name are "ugly", but the point is that it can be hidden anywhere you like, so its internals are as irrelevant as they would be if it was a built-in. Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
Ron Adam <[EMAIL PROTECTED]> wrote: > A "Current" key word would fix this. Or possibly "This" which would be > short for "This object". I think "This" would cause huge confusion, since in other popular language the keyword "this" means (a pointer/reference to) "the instance variable on which the method is being called" -- my use is instead for "the object of the immediate lexically enclosing scope" (a module, class, or function). Implementation wouldn't be trivial in today's CPython, anyway: frames have no references at all to function objects (only to _code_ objects), and class objects don't even exist untill well after their top-level code has long finished running; to make Current possible, these subtle points of semantics would have to be changed in quite a revolutionary way, especially where classes are concerned. Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
James Thiele a écrit : > I'd like to access the name of a function from inside the function. My > first idea didn't work. > > def foo(): > > ... print func_name > ... > foo() > > Traceback (most recent call last): > File "", line 1, in ? > File "", line 2, in foo > NameError: global name 'func_name' is not defined > > My second attempt works but looks ugly. > > def foo(): > > ... import inspect > ... print inspect.stack()[0][3] > ... > foo() > > foo > > Is there a standard way of getting the name of a function from inside > the function? > You've already got good answers. Now here's another workaround: class _FooFunction(object): def __call__(self): print self.__class__.__name__ foo = _FooFunction() -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
Alex Martelli wrote: > Personally, I'd rather have a 3.0 keyword referring to "the current > object" (module for module toplevel code, class for classbody toplevel > code, function for code within a function) -- say for the sake of > argument the keyword is 'current'; this would allow current.__name__ to > have the obvious meaning, and would also allow a few more neat things > (such as natural access to current.__doc__). That was my thought too, that what is really desired is a *obvious* way to get a dependable reference to the current function as you describe here. A quick experiment... with an obvious result: def foo(): print foo.__name__ > ... foo() > foo boo = foo boo() > foo boo.__name__ > 'foo' foo = None boo() > Traceback (most recent call last): > File "", line 1, in ? > File "", line 1, in foo > AttributeError: 'NoneType' object has no attribute '__name__' A "Current" key word would fix this. Or possibly "This" which would be short for "This object". This may also relate to suggestions to reduce the need for having self in the argument list of methods. So if a keyword "This" could mean this method or function, then "Self" could mean this class. Hmmm, methods that use "Self" in this way might run into problems, but I havn't had enough coffee to think it though. ;-) Cheers, Ron -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
Ben Finney <[EMAIL PROTECTED]> wrote: > "James Thiele" <[EMAIL PROTECTED]> writes: > > > I'd like to access the name of a function from inside the function. > > A function, like most other objects in Python, can have any number of > names bound to it without the object being informed. Any of those Yes, but, quite independent of the 0+ names BOUND to the object, function objects, like class and module objects, have ONE "true" name (which may or may not coincide with one of those bound to the object, if any) -- the special attribute __name__ (AKA func_name for function objects only, but I'll stick with __name__ which applies uniformly). Code in a module can get the module's name by simply accessing global variable __name__. I see nothing untowards in a desire to access __name__ from code within a function or a class body, getting the name of the function or the class respectively rather than the name of the module they're in... it's just not implemented that way (and can't be changed until Python 3.0 for backwards compatibility). But proposals for 3.0 can be entertained. Personally, I'd rather have a 3.0 keyword referring to "the current object" (module for module toplevel code, class for classbody toplevel code, function for code within a function) -- say for the sake of argument the keyword is 'current'; this would allow current.__name__ to have the obvious meaning, and would also allow a few more neat things (such as natural access to current.__doc__). But if the OP is looking for a Python 2.* solution, then sys._getframe or module inspect are the only way to go, be they "ugly" as he considers them, or not. Alex -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
On Sun, 26 Mar 2006 10:19:36 +1000, Ben Finney wrote: > "James Thiele" <[EMAIL PROTECTED]> writes: > >> I'd like to access the name of a function from inside the function. > > A function, like most other objects in Python, can have any number of > names bound to it without the object being informed. Any of those > names can then be used to reference the object, and the object has no > way of knowing by what name it was referenced. > > Because of this fallacy, "You keep using that word. I do not think it means what you think it means." *wink* > it's generally considered bad programming > style to want to know "the" name of the current object from inside > that object. I agree whole-heartedly with Ben's sentiments here, although I can also point out by example why it might be useful for a function to know it's own name: def Ackermann(i, j): """Returns the Ackermann function of integers i and j. The Ackermann function is an example of a function which grows at a much faster than exponential rate. Ackermann(i, j) for i > 2 grows even more quickly than 2**2**2**...**2 (where there are j exponents). It is an example of a recursive function which is not primitively recursive and was discovered by the German mathematician Wilhelm Ackermann in 1928. >>> Ackermann(1, 1) 2 >>> Ackermann(2, 2) 16 >>> Ackermann(2, 3) 65536 The Ackermann function is not defined for i,j <= 0. See http://en.wikipedia.org/wiki/Ackermann_function and 'Introduction to Algorithms' by Thomas H Cormen, Charles E Leiserson, Ronald L Rivest, pp. 451-453. """ if i < 0 or j < 0: raise ValueError( "arguments to the Ackermann function must be positive") if i == 1: return 2**j if j == 1: return Ackermann(i-1, 2) return Ackermann(i-1, Ackermann(i, j-1)) Notice that if you change the name of the function, you have to change it in no less than three places in the function definition and four places in the __doc__ string, but a global search and replace is too greedy and will change too much. As a general principle, it is considered best practice to code in such a way that if you change something, you only need to change it in one place. I guess that the Original Poster wants some magic that allows functions to do this: def Ackermann(i, j): """Returns the Ackermann function of integers i and j. The Ackermann function is an example of a function which grows at a much faster than exponential rate. %MAGIC(i, j) for i > 2 grows even more quickly than 2**2**2**...**2 (where there are j exponents). It is an example of a recursive function which is not primitively recursive and was discovered by the German mathematician Wilhelm Ackermann in 1928. >>> %MAGIC(1, 1) 2 >>> %MAGIC(2, 2) 16 >>> %MAGIC(2, 3) 65536 The Ackermann function is not defined for i,j <= 0. See http://en.wikipedia.org/wiki/Ackermann_function and 'Introduction to Algorithms' by Thomas H Cormen, Charles E Leiserson, Ronald L Rivest, pp. 451-453. """ if i < 0 or j < 0: raise ValueError( "arguments to the Ackermann function must be positive") if i == 1: return 2**j if j == 1: return %MAGIC(i-1, 2) return %MAGIC(i-1, %MAGIC(i, j-1)) Now he can easily rename "Ackermann" to "Ack" and need only make the change in one place. I suspect that the correct solution to the O.P.'s problem is to think carefully about the names of your functions in advance. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
"James Thiele" <[EMAIL PROTECTED]> writes: > I'd like to access the name of a function from inside the function. A function, like most other objects in Python, can have any number of names bound to it without the object being informed. Any of those names can then be used to reference the object, and the object has no way of knowing by what name it was referenced. Because of this fallacy, it's generally considered bad programming style to want to know "the" name of the current object from inside that object. What is it you're trying to achieve? -- \ "Unix is an operating system, OS/2 is half an operating system, | `\ Windows is a shell, and DOS is a boot partition virus." -- | _o__) Peter H. Coffin | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
OK. But that's just as ugly as my attempt. -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
James Thiele wrote: > I'd like to access the name of a function from inside the function. http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66062 Kent -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing func_name from inside a function
James Thiele wrote: > Is there a standard way of getting the name of a function from inside > the function? No, there isn't. Martin -- http://mail.python.org/mailman/listinfo/python-list
Accessing func_name from inside a function
I'd like to access the name of a function from inside the function. My first idea didn't work. >>> def foo(): ... print func_name ... >>> foo() Traceback (most recent call last): File "", line 1, in ? File "", line 2, in foo NameError: global name 'func_name' is not defined My second attempt works but looks ugly. >>> def foo(): ... import inspect ... print inspect.stack()[0][3] ... >>> foo() foo Is there a standard way of getting the name of a function from inside the function? -- http://mail.python.org/mailman/listinfo/python-list
