On Apr 26, 1:22 pm, Jean-Paul Calderone <[EMAIL PROTECTED]> wrote: > On 26 Apr 2007 20:05:45 +0200, Neil Cerutti <[EMAIL PROTECTED]> wrote: > > > > > > >On 2007-04-26, Steven Howe <[EMAIL PROTECTED]> wrote: > >> [EMAIL PROTECTED] wrote: > >>>> Well, why do some things in the library have to be functions, > >>>> and other things have to be class methods? > > >> Perhaps because some things are more naturally function like? > >> For 'instance' (pardon the pun), functions shouldn't retain > >> data. They perform an operation, return data and quit. While > >> retaining data is a feature of an class/instance. > > >Functions do retain data. Classes and instances are just a > >convenient notation. ;) > > > [snip] > > >Python's scoping rules make certain kinds of functional idioms > >hard to use, though. I'm not sure how to get the following to > >work in Python using functions: > > >>>> def account(s): > >... b = s > >... def add(a): > >... b += a > >... def balance(): > >... return b > >... return add, balance > >... > >>>> add, balance = account(100) > >>>> balance() > >100 > >>>> add(5) > >Traceback (most recent call last): > > File "<stdin>", line 1, in ? > > File "<stdin>", line 4, in add > >UnboundLocalError: local variable 'b' referenced before assignment > > >Anyhow, it doesn't work, but you can see how closely it resembles > >a class definition. > > Use the outfix closure operator, []: > > >>> def account(s): > ... b = [s] > ... def add(a): > ... b[0] += a > ... def balance(): > ... return b[0] > ... return add, balance > ... > >>> add, balance = account(100) > >>> add(5) > >>> balance() > 105 > >>> > > ;) > > Jean-Paul- Hide quoted text - > > - Show quoted text -
Check out the Percent class I posted at http://www.programmingforums.org/forum/f43-python/t12461-arithmetic-by-percentage.html#post123290. It allows you to write code like: discount = Percent(20) origprice = 35.00 saleprice = origprice - discount -- Paul -- http://mail.python.org/mailman/listinfo/python-list
