Re: multiple breaks

2008-11-15 Thread Robert Lehmann 
On Thu, 13 Nov 2008 02:16:32 -0800, Chris Rebert wrote:

 On Thu, Nov 13, 2008 at 2:07 AM, TP [EMAIL PROTECTED]
 wrote:

 In the following example, is this possible to affect the two iterators
 to escape the two loops once one j has been printed:

 Non-exception alternative:
 
 done = False
 for i in range(5):
for j in range(i):
   print j
 done = True
 break
 if done:
 break

Another alternative is explicitly jumping in the outer loop::

  for i in range(5): # use xrange for larger ranges
  for j in range(i):
  print j
  break
  else:
  continue # applies already to the outer loop
  break

HTH,

-- 
Robert Stargaming Lehmann
--
http://mail.python.org/mailman/listinfo/python-list

Re: multiple breaks

2008-11-13 Thread Marc 'BlackJack' Rintsch 
On Thu, 13 Nov 2008 11:07:25 +0100, TP wrote:

 According to this page, the best way is to modify the loop by affecting
 the variables that are tested in the loops. Otherwise, use exception:
 
 If, for some reason, the terminating conditions can't be worked out,
 exceptions are a fall-back plan.
 
 In the following example, is this possible to affect the two iterators
 to escape the two loops once one j has been printed:
 
 for i in range(5):
 for j in range(i):
print j
# I would type break 2 in shell bash # In C, I would set j=i-1
and i=4
# In Python, is this possible to affect the two iterators?
 
 Or the only means is to use exception?

You could put the code into its own, maybe local, function and use 
``return``.

Ciao,
Marc 'BlackJack' Rintsch
--
http://mail.python.org/mailman/listinfo/python-list

Re: multiple breaks

2008-11-13 Thread Peter Otten 
TP wrote:

 Hi everybody,
 
 Several means to escape a nested loop are given here:
 

http://stackoverflow.com/questions/189645/how-to-break-out-of-multiple-loops-in-python
 
 According to this page, the best way is to modify the loop by affecting
 the variables that are tested in the loops. Otherwise, use exception:
 
 If, for some reason, the terminating conditions can't be worked out,
 exceptions are a fall-back plan.
 
 In the following example, is this possible to affect the two iterators to
 escape the two loops once one j has been printed:
 
 for i in range(5):
 for j in range(i):
print j
# I would type break 2 in shell bash
# In C, I would set j=i-1 and i=4
# In Python, is this possible to affect the two iterators?
 
 Or the only means is to use exception?

Here's one way to turn multiple iterators into a single one:

def pairs(n):
for i in range(n):
for k in range(i):
yield i, k

for i, k in pairs(5):
print i, k

I've yet to see an example where a multi-level break would improve the
code's readability. It is typically a speed hack.

Peter

PS: Have a look into the itertools if you consider that approach.
--
http://mail.python.org/mailman/listinfo/python-list

Re: multiple breaks

2008-11-13 Thread Chris Rebert 
On Thu, Nov 13, 2008 at 2:07 AM, TP [EMAIL PROTECTED] wrote:
 Hi everybody,

 Several means to escape a nested loop are given here:

 http://stackoverflow.com/questions/189645/how-to-break-out-of-multiple-loops-in-python

 According to this page, the best way is to modify the loop by affecting the
 variables that are tested in the loops. Otherwise, use exception:

 If, for some reason, the terminating conditions can't be worked out,
 exceptions are a fall-back plan.

 In the following example, is this possible to affect the two iterators to
 escape the two loops once one j has been printed:


Non-exception alternative:

done = False
 for i in range(5):
for j in range(i):
   print j
done = True
break
   # I would type break 2 in shell bash
   # In C, I would set j=i-1 and i=4
   # In Python, is this possible to affect the two iterators?
if done:
break

 Or the only means is to use exception?

No, you could add a boolean variable and a break condition like above.

Cheers,
Chris
-- 
Follow the path of the Iguana...
http://rebertia.com


 Thanks in advance

 Julien

 --
 python -c print ''.join([chr(154 - ord(c)) for c in '*9(9(18%.91+,\'Z
 (55l4('])

 When a distinguished but elderly scientist states that something is
 possible, he is almost certainly right. When he states that something is
 impossible, he is very probably wrong. (first law of AC Clarke)
 --
 http://mail.python.org/mailman/listinfo/python-list

--
http://mail.python.org/mailman/listinfo/python-list

multiple breaks

2008-11-13 Thread TP 
Hi everybody,

Several means to escape a nested loop are given here:

http://stackoverflow.com/questions/189645/how-to-break-out-of-multiple-loops-in-python

According to this page, the best way is to modify the loop by affecting the
variables that are tested in the loops. Otherwise, use exception:

If, for some reason, the terminating conditions can't be worked out,
exceptions are a fall-back plan.

In the following example, is this possible to affect the two iterators to
escape the two loops once one j has been printed:

for i in range(5):
for j in range(i):
   print j
   # I would type break 2 in shell bash
   # In C, I would set j=i-1 and i=4
   # In Python, is this possible to affect the two iterators?

Or the only means is to use exception?

Thanks in advance

Julien

-- 
python -c print ''.join([chr(154 - ord(c)) for c in '*9(9(18%.91+,\'Z
(55l4('])

When a distinguished but elderly scientist states that something is
possible, he is almost certainly right. When he states that something is
impossible, he is very probably wrong. (first law of AC Clarke)
--
http://mail.python.org/mailman/listinfo/python-list

Re: multiple breaks

2008-11-13 Thread Steve Holden 
Chris Rebert wrote:
 On Thu, Nov 13, 2008 at 2:07 AM, TP [EMAIL PROTECTED] wrote:
 Hi everybody,

 Several means to escape a nested loop are given here:

 http://stackoverflow.com/questions/189645/how-to-break-out-of-multiple-loops-in-python

 According to this page, the best way is to modify the loop by affecting the
 variables that are tested in the loops. Otherwise, use exception:

 If, for some reason, the terminating conditions can't be worked out,
 exceptions are a fall-back plan.

 In the following example, is this possible to affect the two iterators to
 escape the two loops once one j has been printed:

 
 Non-exception alternative:
 
 done = False
 for i in range(5):
for j in range(i):
   print j
 done = True
 break
   # I would type break 2 in shell bash
   # In C, I would set j=i-1 and i=4
   # In Python, is this possible to affect the two iterators?
 if done:
 break
 Or the only means is to use exception?
 
 No, you could add a boolean variable and a break condition like above.
 
Though I would have to ask why you would want to. An exception seems
rather cleaner, though of course tastes vary.

regards
 Steve
-- 
Steve Holden+1 571 484 6266   +1 800 494 3119
Holden Web LLC  http://www.holdenweb.com/

--
http://mail.python.org/mailman/listinfo/python-list