Re: [Tutor] scope/namespaces
On 4/24/07, ammar azif [EMAIL PROTECTED] wrote: i am able to access the variable declared in that loop after the loop finishes which i am not able to do in languages like c/c++ or java. Is it different in python? I'm not sure what you mean with different, but the loop-variable is not destroyed upon the exit of the for-loop: z Traceback (most recent call last): File stdin, line 1, in ? NameError: name 'z' is not defined for z in (1,2,3): pass ... print z 3 -- - Rikard - http://bos.hack.org/cv/ ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] scope/namespaces
ammar azif wrote: Something in python disturbs me , when i write a for loop, i am able to access the variable declared in that loop after the loop finishes which i am not able to do in languages like c/c++ or java. Is it different in python? Yes, it is different. In Python a block is not a scope. Names bound within the block, including the loop variable, are accessible outside the block. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] scope/namespaces
Sorry about that kent. I just realized I emailed you directly. Ezra On 4/24/07, Kent Johnson [EMAIL PROTECTED] wrote: ammar azif wrote: Something in python disturbs me , when i write a for loop, i am able to access the variable declared in that loop after the loop finishes which i am not able to do in languages like c/c++ or java. Is it different in python? Yes, it is different. In Python a block is not a scope. Names bound within the block, including the loop variable, are accessible outside the block. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- Ezra Taylor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] scope/namespaces
Ezra Taylor wrote: Hello Kent: How can we limit this functionality so that python behaves similar to other know languages. Maybe I should be asking what are the benifits of allow variables not being bound to a block of code. Why is this a problem? Don't try to turn Python into Java, you might as well stay with Java. One advantage is, you can define a variable in a conditional block or a try block without having to declare it first. For example: if something: x = 3 else: x = 5 or try: x = foo() finally: cleanup() # do something with x It has long annoyed my that in Java these snippets would have to be prefixed with int x; Kent Ezra On 4/24/07, *Kent Johnson* [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: ammar azif wrote: Something in python disturbs me , when i write a for loop, i am able to access the variable declared in that loop after the loop finishes which i am not able to do in languages like c/c++ or java. Is it different in python? Yes, it is different. In Python a block is not a scope. Names bound within the block, including the loop variable, are accessible outside the block. Kent ___ Tutor maillist - Tutor@python.org mailto:Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- Ezra Taylor ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] scope/namespaces
ammar azif [EMAIL PROTECTED] wrote Something in python disturbs me , when i write a for loop, i am able to access the variable declared in that loop after the loop finishes which i am not able to do in languages like c/c++ or java. That's a very recent change to C/C++ (1999 apparently), you used to be able to do that. In fact I hadn't realised that you couldn't any more! It was only when I wrote a test program I discovered you were right... Is it different in python? Yes. Once you create a name within a scope it stays there and loops or code blocks are not a separate scope in Python -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] scope/namespaces
Ezra Taylor wrote: How can we limit this functionality so that python behaves similar to other know languages. There are many other languages that work like Python. Including the original versions of C and C++... And other languages that don't have explicit loop constructs at all! Others only have while loops... Maybe I should be asking what are the benifits of allow variables not being bound to a block of code. For one thing you can find out how far a loop got to if it was exited via a break. for n in range(25): if doit(item[n]) == False: break print 'The loop stopped at item', n There are lots of things that languages do differently, otherwise there would be no point in having different languages! Embrace the differences as an opportunity to see things differently. ;-) -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] scope/namespaces
Am I wrong in my memory? When I was a wee lad prior to 99 for sure),
I thought I would initialize my loops with:
for (int x=0; x 10; x++) {
}
I am rapidly veering off topic.
On 4/24/07, Alan Gauld [EMAIL PROTECTED] wrote:
Correcting my own post!
Alan Gauld [EMAIL PROTECTED] wrote
That's a very recent change to C/C++ (1999 apparently),
Actually only a recent change in C. Its always been true of C++.
But in C up until recently(*) you couldn't define a loop
variable in the loop it had to be outside:
int x;
for (x=0;)
(*)I'm not sure whether the C++ style loop definition was
introduced in the original ANSI standard or the later
revision (none of my books malke it clear), but I think it was
the revision.
But C++ always had loop variables as part of block scope.
Sory for any confusion,
Alan G.
___
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
___
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] scope/namespaces
Ben Sherman schreef:
Am I wrong in my memory? When I was a wee lad prior to 99 for sure),
I thought I would initialize my loops with:
for (int x=0; x 10; x++) {
}
If that was in C, it must have been a special feature of your compiler.
--
If I have been able to see further, it was only because I stood
on the shoulders of giants. -- Isaac Newton
Roel Schroeven
___
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] scope/namespaces
Ben Sherman [EMAIL PROTECTED] wrote
Am I wrong in my memory? When I was a wee lad prior to 99 for
sure),
I thought I would initialize my loops with:
for (int x=0; x 10; x++) {
You certainly could in C++ but I'm less sure about C.
You certainly couldn't do that in C prior to ANSI C
(in 1991/2?). However I don't think the C++ bits got
incorporated into C until the C update in '99. However
that didn't stop some compilers supporting them.
For example the C++ // comment style was supported
by most ANSI compilers even though it wasn't in the
original ANSI standard.
I am rapidly veering off topic.
Me too :-)
Alan G.
Who hasn't used vanilla C in anger for at least 10 years!
(And C++ for 4 or 5...)
___
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
