[Tutor] Re: Re: Self referencing within a dictionary
John Fouhy wrote on Sun, 03 Apr 2005 09:53:56 +1200: > Andrei wrote: >> Liam Clarke wrote on Sat, 2 Apr 2005 22:12:49 +1200: >>>I know that as above doesn't work, but was just wondering if it's >>>possible, and if it's a Bad Thing? >> Max has already shown it's possible. Whether it's a Bad Thing... I don't >> see why it would be. But I also can't imagine right now any realistic cases >> where it would be useful to have a dictionary contain itself as a value. > > It wouldn't contain itself as a value. My mistake, I read the messages hastily and missed the ['a']. It was a more interesting question that way ;). -- Yours, Andrei = Real contact info (decode with rot13): [EMAIL PROTECTED] Fcnz-serr! Cyrnfr qb abg hfr va choyvp cbfgf. V ernq gur yvfg, fb gurer'f ab arrq gb PP. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] What is the best book to start? - Many Thanks!
Dear Hoffmann, I am also a Newbie and I am currently going through "A Byte of Python" tutorial from Swaroop C H. http://www.byteofpython.info/download?PHPSESSID=c0d52343d90f69f25942f49df9ae7944 If you are completely new to programming like me, you will find that this tutorial is excellent. Good luck JC ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Self referencing within a dictionary
> foo = {'a':1, 'b':2, 'c':foo['a']}
TRy
foo = {'a':1, 'b':2}
foo['c'] = foo['a']
The only reasobn it ddidn't work before was that
foo didn't exist at the time you tried to add the reference.
foo['c'] is just a reference to whatever foo['a'] references.
foo['d'] = foo
is a tad more interesting however.
especially if you do
foo['d']['d']['b'] = 42
As a mental excercise...
Now what does foo look like? :-)
> I know that as above doesn't work, but was just wondering if it's
> possible, and if it's a
> Bad Thing?
It's possible and may be a good thing depending on what you are trying
to do. It certainly shouldn't be a regular thing!
Alan G.
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[Tutor] Script (Python) for Zope
Hello, I am looking for a Python-script for Zope which counts the objects (files) in the current folder and all its subfolders, but I don't know how to implement this script. Can somebody help me, please? Or ist there a newsgroup/mailing list which can help me to find a solution for this problem? Thanks. Mike___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] [HELP]how to test properties of a file
Dear all, Here is a simple question. But I can't find a simple answer. How to test if a file is readable, executalbe or writable, especially, writable? -- With best wishes! Shidai ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] [HELP]how to test properties of a file
Tthe simplest, IMHO, is : try: f = file(filename, "w") [...] except IOError: print "The file is not writable" Of course, not that this method empty the file if it is writable ! The best is to just put your IO code in such a try block ... That way, you're sure the file has the right mode. If you don't want to open the file to detect its mode, then you need to use the os and stat modules together ... Pierre Shidai Liu a écrit : Dear all, Here is a simple question. But I can't find a simple answer. How to test if a file is readable, executalbe or writable, especially, writable? -- Pierre Barbier de Reuille INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP Botanique et Bio-informatique de l'Architecture des Plantes TA40/PSII, Boulevard de la Lironde 34398 MONTPELLIER CEDEX 5, France tel : (33) 4 67 61 65 77fax : (33) 4 67 61 56 68 ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] [HELP]how to test properties of a file
On Apr 3, 2005 6:42 PM, Pierre Barbier de Reuille <[EMAIL PROTECTED]> wrote: > Tthe simplest, IMHO, is : > > try: > f = file(filename, "w") > [...] > except IOError: > print "The file is not writable" > > Of course, not that this method empty the file if it is writable ! The > best is to just put your IO code in such a try block ... That way, > you're sure the file has the right mode. > > If you don't want to open the file to detect its mode, then you need to > use the os and stat modules together ... > > Pierre > I thought of this first. But I wasn't sure if it's the simplest. Thanks for your help! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Re: If elif not working in comparison
On Mar 29, 2005 3:06 AM, C Smith <[EMAIL PROTECTED]> wrote:
> If you have Python 2.4 you might want to check out the decimal type
> that is now part of the language. There is a description at
>
> http://www.python.org/doc/2.4/whatsnew/node9.html
>
> >>> import decimal
> >>> a = decimal.Decimal('35.72')
> >>> b = decimal.Decimal('1.73')
> >>> a+b
> Decimal("37.45")
> >>> a-b
> Decimal("33.99")
> >>> a*b
> Decimal("61.7956")
> >>> a/b
> Decimal("20.64739884393063583815028902")
>
Would I used an if else: construction to determine where the INR value
lay and decide what precentage to increase it by?
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[Tutor] Operator Overloading
Following an example from a book, I'm getting an unexpected outcome. The point of exercise is to extend operator overloading methods from a superclass and track the method calls. Here's the code, class MyList: def __init__(self, start): self.wrapped = [ ] for x in start: self.wrapped.append(x) def __add__(self, other): return MyList(self.wrapped + other) def __len__(self): return len(self.wrapped) = from module import MyList class MyListSub(MyList): calls = 0 def __init__(self, start): self.adds = 0 MyList.__init__(self, start) def __add__(self, other): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__add__(self, other) def __len__(self): MyListSub.calls = MyListSub.calls + 1 self.adds = self.adds + 1 return MyList.__len__(self) def stats(self): return self.calls, self.adds This is not my code but is taken from the book I'm working with. My problem is that whenever I call to the __add__ method the counters increase by 2 while calls the __len__ method increase the counters by 1 as expected. What I've concluded is that the method which overloads and arithmetic operations executes the counter statements twice while the method which overloads a sequencing operation executes the counter statements only once. Otherwise, I can see no difference between the two methods. Here's an example, >>> A = MyListSub([1, 2, 3]) >>> A.stats() (0, 0) >>> len(A) 3 >>> A.stats() (1, 1) >>> A + [4, 5, 6] [1, 2, 3, 4, 5, 6] >>> A.stats() (3, 3) I'm stumped and and would appreciate any help. Kevin ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
