Re: Partial Function Application -- Advantages over normal function?
On 19/07/11 00:33, Thomas 'PointedEars' Lahn wrote: Thomas 'PointedEars' Lahn wrote: Dave Angel wrote: On 01/-10/-28163 02:59 PM, Terry Reedy wrote: def makeadder(y) def _add(x): return x+y add2 = makeadder(2) A couple of typos in that code: def makeaddr(y): def _add(x): return x+y return _add I agree about the `return' statement, but not about the factory name; this has nothing to do with addresses (addr). Supplemental: The above can be simplified to def makeadder(y): return lambda x: x + y In turn: makeadder = lambda y: lambda x: x + y Smells of Haskell. -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
On Tue, Jul 19, 2011 at 11:52 AM, Thomas Jollans t...@jollybox.de wrote: On 19/07/11 00:33, Thomas 'PointedEars' Lahn wrote: Thomas 'PointedEars' Lahn wrote: Dave Angel wrote: On 01/-10/-28163 02:59 PM, Terry Reedy wrote: def makeadder(y) def _add(x): return x+y add2 = makeadder(2) A couple of typos in that code: def makeaddr(y): def _add(x): return x+y return _add I agree about the `return' statement, but not about the factory name; this has nothing to do with addresses (addr). Supplemental: The above can be simplified to def makeadder(y): return lambda x: x + y In turn: makeadder = lambda y: lambda x: x + y Smells of Haskell. -- http://mail.python.org/mailman/listinfo/python-list Hi All, Thanks guys for the reply. I now understand something. Since Im a newbie, let me read over and over so that I will get the complete picture of everyone's idea. :-) Regards, Kurian Thayil. -- http://mail.python.org/mailman/listinfo/python-list
Re: Re: Partial Function Application -- Advantages over normal function?
On 01/-10/-28163 02:59 PM, Thomas 'PointedEars' Lahn wrote: Dave Angel wrote: On 01/-10/-28163 02:59 PM, Terry Reedy wrote: def makeadder(y) def _add(x): return x+y add2 = makeadder(2) A couple of typos in that code: def makeaddr(y): def _add(x): return x+y return _add I agree about the `return' statement, but not about the factory name; this has nothing to do with addresses (addr). The two changes that I made deliberately were adding the colon and adding the return statement. I'm not sure how the name got changed; that was accidental. DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
On Tue, Jul 19, 2011 at 12:22 AM, Thomas Jollans t...@jollybox.de wrote: Supplemental: The above can be simplified to def makeadder(y): return lambda x: x + y In turn: makeadder = lambda y: lambda x: x + y That's not an improvement. lambda is for making anonymous functions. If you're going to construct a lambda and bind it to a name, you should just use def. -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
On 7/19/2011 6:07 AM, Dave Angel wrote: On 01/-10/-28163 02:59 PM, Thomas 'PointedEars' Lahn wrote: Dave Angel wrote: On 01/-10/-28163 02:59 PM, Terry Reedy wrote: def makeadder(y) def _add(x): return x+y add2 = makeadder(2) A couple of typos in that code: def makeaddr(y): def _add(x): return x+y return _add I agree about the `return' statement, but not about the factory name; this has nothing to do with addresses (addr). The two changes that I made deliberately were adding the colon and adding the return statement. I'm not sure how the name got changed; that was accidental. Anyway, my apologies for posting quickly without testing and without saying so. I know better and too often leave in mistakes when I do. -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
On 19/07/11 18:49, Ian Kelly wrote: On Tue, Jul 19, 2011 at 12:22 AM, Thomas Jollans t...@jollybox.de wrote: Supplemental: The above can be simplified to def makeadder(y): return lambda x: x + y In turn: makeadder = lambda y: lambda x: x + y That's not an improvement. lambda is for making anonymous functions. If you're going to construct a lambda and bind it to a name, you should just use def. No, it's not an improvement. It's an illustration. -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
On Tue, Jul 19, 2011 at 10:58 AM, Thomas Jollans t...@jollybox.de wrote: No, it's not an improvement. It's an illustration. I get that. The difference I pointed out between your simplification and the other Thomas's is the reason why yours would be unpythonic whilst his is fine. -- http://mail.python.org/mailman/listinfo/python-list
Partial Function Application -- Advantages over normal function?
Hi, I am a newbie in python and would like to learn GUI programming. I would like to know what exactly is Partial Function Applicaton (functool.partial())? Or how is it advantageous compared to normal functions? Or is there any advantange? Thanks in advance. Regards, Kurian Thayil. -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
Partial function application (or currying) is the act of taking a function with two or more parameters, and applying some of the arguments in order to make a new function. The hello world example for this seems to be this: Let's say you have a function called `add`, that takes two parameters: def add(left, right): ... return left + right Now let's say you want a function that always adds 2 to a number you give it. You can use partial function application to do this: from functools import partial add2 = partial(add, right=2) Now, you have a new function, `add2`, that takes one parameter: add2(4) 6 --- Paul Woolcock pwool...@gmail.com On Mon, Jul 18, 2011 at 6:13 AM, Kurian Thayil kurianmtha...@gmail.com wrote: Hi, I am a newbie in python and would like to learn GUI programming. I would like to know what exactly is Partial Function Applicaton (functool.partial())? Or how is it advantageous compared to normal functions? Or is there any advantange? Thanks in advance. Regards, Kurian Thayil. -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
Kurian Thayil wrote: Hi, I am a newbie in python and would like to learn GUI programming. I would like to know what exactly is Partial Function Applicaton (functool.partial())? Or how is it advantageous compared to normal functions? Or is there any advantange? Thanks in advance. It is mostly for functional programming style. But one lucky side-effect of the implementation is that partial functions *may* sometimes be faster than the alternative written in pure Python, provided the original function is written in C: from functools import partial from operator import add def add_one(x): return add(1, x) # Like 1+x add_two = partial(add, 2) from timeit import Timer setup = from __main__ import add_one, add_two t1 = Timer(add_one(42), setup) t2 = Timer(add_two(42), setup) And in action: t1.timeit() 0.7412619590759277 t2.timeit() 0.3557558059692383 So in this example, the partial function is about twice as fast as the one written in Python. This does not necessarily apply for all functions, but it sometimes is useful. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
Partial can be used in a GUI program, like Tkinter, to send arguments to functions. There are other ways to do that as well as using partial. The following program uses partial to send the color to the change_buttons function. from Tkinter import * from functools import partial class App: def __init__(self, parent): self.my_parent = parent self.my_parent.geometry(200x100+10+10) self.R = list() for ctr, color in enumerate((Red, Blue, Green)): btn = Radiobutton(self.my_parent, text=color, value=ctr+1, command=partial(self.change_buttons, color)) btn.grid(row = 2, column = ctr+1) btn.deselect() self.R.append(btn) self.R[0].select() self.change_buttons(Red) def change_buttons(self, color): self.my_parent.configure(bg=color) for btn in self.R: btn.configure(bg=color) if __name__ == __main__: root = Tk() root.title (Color Option) app = App(root) root.mainloop() -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
On 7/18/2011 8:24 AM, Paul Woolcock wrote: Partial function application (or currying) is the act of taking a function with two or more parameters, and applying some of the arguments in order to make a new function. The hello world example for this seems to be this: Let's say you have a function called `add`, that takes two parameters: def add(left, right): ... return left + right Now let's say you want a function that always adds 2 to a number you give it. You can use partial function application to do this: from functools import partial add2 = partial(add, right=2) Now, you have a new function, `add2`, that takes one parameter: add2(4) Or you can directly write def add2(x): return x + 2 or more generically def makeadder(y) def _add(x): return x+y add2 = makeadder(2) functool.partial is essential a generic version of makeadder in that it also abstract the function/operator. It is useful when one has a function but perhaps not the source. It's limitation is that args are frozen left to right while the above example freezes the right operand. -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
On 7/18/2011 3:23 PM, woooee wrote: Partial can be used in a GUI program, like Tkinter, to send arguments to functions. There are other ways to do that as well as using partial. The following program uses partial to send the color to the change_buttons function. from Tkinter import * from functools import partial class App: def __init__(self, parent): self.my_parent = parent self.my_parent.geometry(200x100+10+10) self.R = list() for ctr, color in enumerate((Red, Blue, Green)): btn = Radiobutton(self.my_parent, text=color, value=ctr+1, command=partial(self.change_buttons, color)) btn.grid(row = 2, column = ctr+1) This is a nice illustration. For future reference: enumerate now takes a start value as second parameter. Given as 1, you do not need to remember to add 1 for each usage. for ctr, color in enumerate((Red, Blue, Green),1): btn = Radiobutton(self.my_parent, text=color, value=ctr, command=partial(self.change_buttons, color)) btn.grid(row = 2, column = ctr) btn.deselect() self.R.append(btn) self.R[0].select() self.change_buttons(Red) def change_buttons(self, color): self.my_parent.configure(bg=color) for btn in self.R: btn.configure(bg=color) if __name__ == __main__: root = Tk() root.title (Color Option) app = App(root) root.mainloop() -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
On 01/-10/-28163 02:59 PM, Terry Reedy wrote: On 7/18/2011 8:24 AM, Paul Woolcock wrote: Partial function application (or currying) is the act of taking a function with two or more parameters, and applying some of the arguments in order to make a new function. The hello world example for this seems to be this: snip def makeadder(y) def _add(x): return x+y add2 = makeadder(2) snip A couple of typos in that code: def makeaddr(y): def _add(x): return x+y return _add DaveA -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
Dave Angel wrote: On 01/-10/-28163 02:59 PM, Terry Reedy wrote: def makeadder(y) def _add(x): return x+y add2 = makeadder(2) A couple of typos in that code: def makeaddr(y): def _add(x): return x+y return _add I agree about the `return' statement, but not about the factory name; this has nothing to do with addresses (addr). -- PointedEars Bitte keine Kopien per E-Mail. / Please do not Cc: me. -- http://mail.python.org/mailman/listinfo/python-list
Re: Partial Function Application -- Advantages over normal function?
Thomas 'PointedEars' Lahn wrote: Dave Angel wrote: On 01/-10/-28163 02:59 PM, Terry Reedy wrote: def makeadder(y) def _add(x): return x+y add2 = makeadder(2) A couple of typos in that code: def makeaddr(y): def _add(x): return x+y return _add I agree about the `return' statement, but not about the factory name; this has nothing to do with addresses (addr). Supplemental: The above can be simplified to def makeadder(y): return lambda x: x + y -- PointedEars Bitte keine Kopien per E-Mail. / Please do not Cc: me. -- http://mail.python.org/mailman/listinfo/python-list
