how to compile c-extensions under WinXP?

[severa]

What should I do to be able to compile C-extensions (with python 2.4, 
winXP)? I get an error message, approximately "The .NET Framework SDK 
needs to be installed"; I tried to get something from the Microsoft web 
site, but maybe not the right version (or didn't set some variables), 
since the error remains. Could you please help me (it will need some 
patience with a computer newbie)?

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why no user-def. attributes?

[severa]

I appologize in advance for stupid question, which is:
why are user-defined attributes not allowed for builtin types?
[I guess I undestand why *instances* cannot have them (e.g. then every 
dict would have a dict which would have a dict..), but this is a 
different question]

I can imagine several answers, so I put here those that don't seem 
satisfactory to me :)

1. You can subclass, eg. 
class my_int(int): pass
and then do whatnot, like my_int.__getitem__=some_vicious_function

Here the problem is just that it's easier to write 4 than 
my_int(4), or "ha" than my_string("ha") etc.

2. You would probably want to add new methods, so why don't you 
define a function and then write e.g. dowhatIwant([1,2,3]) instead of
[1,2,3].dowhatIwant() 

That's OK, except for the convenience of special methods like __add__ or 
__iter__

3. It would lead to a confusing code

Oops, maybe I shouldn't have written this one..


Anyway, please let me know the true reason (which is perhaps technical)


Best whishes
Paul


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How to write this iterator?

[severa]

Given a list of iterators, I'd like to have a new one that would 
cyclically walk over the list calling the next() method of the iterators 
(removing any iterator which is exhausted). It should also support adding 
a new iterator to the list; it should be added in front of the current 
position (so that it's called only after all the others). This is what I 
was able to write with my zero python skills (self.iters is the list of 
iterators, self.i is the index of the iterator that should be used next). 
Is there a nicer/more pythonic solution, maybe using generators?


class Liter(object):

def __init__(self, *iters):
self.i=0
self.iters=[iter(x) for x in iters]

def append(self,what):
self.iters.insert(self.i,what)

def __iter__(self):
return self

def next(self):
while True:
try:
result=self.iters[self.i].next()
except StopIteration:
del self.iters[self.i]
except IndexError:
if len(self.iters) is 0:
raise StopIteration
else:
self.i=0
else:
self.i+=1
return result



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Re: How to write this iterator?

[severa]

Sorry, my description was not very good, I meant something behaving as:

>>>example=Liter("abc","12345","XY")
>>>for x in example: print x,

a 1 X b 2 Y c 3 4 5

or for that append() method,

>>>example=Liter("abc", "12345")
>>>for i in range(3): print example.next(),

a 1 b

>>>example.append("XY")
>>>for x in example: print x,

2 c X 3 Y 4 5

Hope this clarifies what I mean

Best regards
Pavol

>A generator version:
>
>def iterconcat (collectionlist):
> for collection in collectionlist:
> for element in collection:
> yield element
>
>Extending collectionlist at runtime will work only with lists and 
>similar collections. And you'll need to keep a reference to it as well. 
>And it would be called after all the others, which matches your 
>description, but not your code.
>
>Daniel

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Re: How to write this iterator?

[severa]

>> Sorry, my description was not very good, I meant something behaving as:
>>
>> >>>example=Liter("abc","12345","XY")
>> >>>for x in example: print x,
>>
>> a 1 X b 2 Y c 3 4 5
>>
>> or for that append() method,
>>
>> >>>example=Liter("abc", "12345")
>> >>>for i in range(3): print example.next(),
>>
>> a 1 b
>>
>> >>>example.append("XY")
>> >>>for x in example: print x,
>>
>> 2 c X 3 Y 4 5

>Check the module I posted on
>http://rafb.net/paste/results/CRT7bS68.html. append() makes things more
>complicated -- mainly because generators don't accept attributes, so it
>has to be wrapped in a class -- but the simple generator (without
>append) is more manageable

Thank you very much for your solution. Actually I needed that append() 
method quite a lot, so maybe my solution (posted at the beginning of this 
thread) was not that stupid :) (to inflate my ego a bit)

Anyway, this is roughly what I used it for; is it a sane use of iterators?

I was looking for the Holy Grail. I had an iterator 'quest' that produced 
either junk that was to be thrown away, or the Holy Grail itself, or 
another iterator of the same kind (that had to be searched for the Holy 
Grail as well). The iterators were potentially infinite. The code was 
rougly:

quest=Liter(quest)
for x in quest:
if is_Holy_Grail(x):
share_and_enjoy(x)
break
elif is_another_iterator(x):
quest.append(x) 


Best regards
P.

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Re: Sudoku solver: reduction + brute force

[Pavol . Severa]

ago wrote:
> Inspired by some recent readings on LinuxJournal and an ASPN recipe, I
> decided to revamp my old python hack... The new code is a combination
> of (2) reduction methods and brute force and it is quite faster than
> the
> ASPN program. If anyone is interested I attached the code in
> http://agolb.blogspot.com/2006/01/sudoku-solver-in-python.html

I suggest trying

input="""
0,0,0,0,9,6,8,0,0
0,0,1,0,0,0,0,7,0
0,2,0,0,0,0,0,0,3
0,3,0,0,0,8,0,0,6
0,0,4,0,2,0,3,0,0
6,0,0,5,0,0,0,8,0
9,0,0,0,0,0,0,5,0
0,7,0,0,0,0,1,0,0
0,0,5,9,4,0,0,0,0"""

your program seems to take too long to solve it.

I think the hard part is not to solve, but rather to create *difficult*
sudoku grids.
But to inflate my ego beyond the known universe, here is my solver
(that solves the avove mentioned grid reasonably fast). I suppose the
only difference is that is uses 3, rather than 2, rules to simplify
before starting tree-like search.



#
#if a copyryght is needed:
#this is pulbic domain, do with it whatever you want
#i.e. most probably nothing
#

class DeadEnd(Exception):
pass

class sudoku(object):

def __init__(self,*args):
self.changed=True
self.possible=[]
if len(args) != 81:
raise ValueError, "need 81 numbers"
for i in args:
if i==0:
self.possible.append(range(1,10))
else:
self.possible.append([i])

def __getitem__(self,(x,y)):
return self.possible[9*x+y]

def __setitem__(self,(x,y),what):
self.possible[9*x+y]=what

def copy(self):
result=sudoku(*(81*[1]))
for i in range(9):
for j in range(9):
result[i,j]=list(self[i,j])
return result

def solved(self):
for i in range(9):
for j in range(9):
if len(self[i,j]) != 1:
return False
return True

def trials(self):
for i,j in ((i,j) for ln in range(2,10)
for i in range(9) for j in range(9)
if len(self[i,j])==ln):
for k in self[i,j]:
new=self.copy()
new[i,j]=[k]
yield new

def clean1(self,x,y):
self.changed=False
if len(self[x,y]) == 1:
return
remove=set()
for places in self.regions(x,y):
missing=set(range(1,10))
for xx,yy in places:
if xx==x and yy==y:
continue
if len(self[xx,yy])==1:
remove.add(self[xx,yy][0])
missing-=set(self[xx,yy])
if missing:
a=missing.pop()
self[x,y]=[a]
self.changed=True
for a in remove:
try:
self[x,y].remove(a)
if not self[x,y]:
raise DeadEnd
self.changed=True
except ValueError:
pass

def clean3(self,out1,out2):
for (o1, o2) in ((out1,out2), (out2,out1)):
remove=set(range(1,10))
for x,y in o1:
remove-=set(self[x,y])
for x,y in o2:
for n in remove:
try:
self[x,y].remove(n)
if not self[x,y]:
raise DeadEnd
self.changed=True
except ValueError:
pass

@staticmethod
def regions(x,y):
return  (((xx,y) for xx in range(9)),
 ((x,yy) for yy in range(9)),
 ((xx,yy) for xx in range(3*(x//3),3*(x//3)+3)
  for yy in range(3*(y//3),3*(y//3)+3)))


@staticmethod
def outs():
for i in range(3):
for j in range(3):
for k in range(3):
out1=[(a+3*i,b+3*j) for a in range(3)
if a is not k for b in range(3)]
out2=[(k+3*i,n) for n in range(9) if n//3!=j]
yield out1, out2
for k in range(3):
out1=[(a+3*i,b+3*j) for a in range(3)
for b in range(3) if b is not k]
out2=[(n,k+3*j) for n in range(9) if n//3!=i]
yield out1, out2

def clean_all(self):
while self.changed:
self.changed=False
for x in range(9):
for y in range(9):
self.clean1(x,y)
for out1,out2 in self.outs():
self.clean3(out1,out2)

def __repr__(self):
result=""
for x in range(9):
for y in range(9):
if len(self[x,y])==1:
haf=self[x,y][0]
else:
haf=self[x,y]
result+=str(haf)+' '
result+='\n'
return result




from collections import deque

cla

Re: Sudoku solver: reduction + brute force

[Pavol . Severa]

ago wrote:
> Inspired by some recent readings on LinuxJournal and an ASPN recipe, I
> decided to revamp my old python hack... The new code is a combination
> of (2) reduction methods and brute force and it is quite faster than
> the
> ASPN program. If anyone is interested I attached the code in
> http://agolb.blogspot.com/2006/01/sudoku-solver-in-python.html

I suggest trying

input="""
0,0,0,0,9,6,8,0,0
0,0,1,0,0,0,0,7,0
0,2,0,0,0,0,0,0,3
0,3,0,0,0,8,0,0,6
0,0,4,0,2,0,3,0,0
6,0,0,5,0,0,0,8,0
9,0,0,0,0,0,0,5,0
0,7,0,0,0,0,1,0,0
0,0,5,9,4,0,0,0,0"""

your program seems to take too long to solve it.

I think the hard part is not to solve, but rather to create *difficult*
sudoku grids.
But to inflate my ego beyond the known universe, here is my solver
(that solves the avove mentioned grid reasonably fast). I suppose the
only difference is that is uses 3, rather than 2, rules to simplify
before starting tree-like search.



#
#if a copyryght is needed:
#this is pulbic domain, do with it whatever you want
#i.e. most probably nothing
#

class DeadEnd(Exception):
pass

class sudoku(object):

def __init__(self,*args):
self.changed=True
self.possible=[]
if len(args) != 81:
raise ValueError, "need 81 numbers"
for i in args:
if i==0:
self.possible.append(range(1,10))
else:
self.possible.append([i])

def __getitem__(self,(x,y)):
return self.possible[9*x+y]

def __setitem__(self,(x,y),what):
self.possible[9*x+y]=what

def copy(self):
result=sudoku(*(81*[1]))
for i in range(9):
for j in range(9):
result[i,j]=list(self[i,j])
return result

def solved(self):
for i in range(9):
for j in range(9):
if len(self[i,j]) != 1:
return False
return True

def trials(self):
for i,j in ((i,j) for ln in range(2,10)
for i in range(9) for j in range(9)
if len(self[i,j])==ln):
for k in self[i,j]:
new=self.copy()
new[i,j]=[k]
yield new

def clean1(self,x,y):
self.changed=False
if len(self[x,y]) == 1:
return
remove=set()
for places in self.regions(x,y):
missing=set(range(1,10))
for xx,yy in places:
if xx==x and yy==y:
continue
if len(self[xx,yy])==1:
remove.add(self[xx,yy][0])
missing-=set(self[xx,yy])
if missing:
a=missing.pop()
self[x,y]=[a]
self.changed=True
for a in remove:
try:
self[x,y].remove(a)
if not self[x,y]:
raise DeadEnd
self.changed=True
except ValueError:
pass

def clean3(self,out1,out2):
for (o1, o2) in ((out1,out2), (out2,out1)):
remove=set(range(1,10))
for x,y in o1:
remove-=set(self[x,y])
for x,y in o2:
for n in remove:
try:
self[x,y].remove(n)
if not self[x,y]:
raise DeadEnd
self.changed=True
except ValueError:
pass

@staticmethod
def regions(x,y):
return  (((xx,y) for xx in range(9)),
 ((x,yy) for yy in range(9)),
 ((xx,yy) for xx in range(3*(x//3),3*(x//3)+3)
  for yy in range(3*(y//3),3*(y//3)+3)))


@staticmethod
def outs():
for i in range(3):
for j in range(3):
for k in range(3):
out1=[(a+3*i,b+3*j) for a in range(3)
if a is not k for b in range(3)]
out2=[(k+3*i,n) for n in range(9) if n//3!=j]
yield out1, out2
for k in range(3):
out1=[(a+3*i,b+3*j) for a in range(3)
for b in range(3) if b is not k]
out2=[(n,k+3*j) for n in range(9) if n//3!=i]
yield out1, out2

def clean_all(self):
while self.changed:
self.changed=False
for x in range(9):
for y in range(9):
self.clean1(x,y)
for out1,out2 in self.outs():
self.clean3(out1,out2)

def __repr__(self):
result=""
for x in range(9):
for y in range(9):
if len(self[x,y])==1:
haf=self[x,y][0]
else:
haf=self[x,y]
result+=str(haf)+' '
result+='\n'
return result




from collections import deque

cla