Debugging Builds

[David Coffin]

Hi,

Is there any documentation concerning the Python debugging builds  
beyond section 1.5 in the Python/C API reference manual and Misc/ 
SpecialBuilds.txt file in the source code?

I'd like to know how people generally go about debugging memory leaks  
in C extensions.

Thanks,
David




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Re: Beautiful Soup Question: Filtering Images based on their width and height attributes

[David Coffin]

> Hello,
>
> I want to extract some image links from different html pages, in
> particular i want extract those image tags which height values are
> greater than 200. Is there an elegant way in BeautifulSoup to do this?

Yes.

soup.findAll(lambda tag: tag.name=="img" and tag.has_key("height")  
and int(tag["height"]) > 200)


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changing value of 'self' when subclassing int

[David Coffin]

I'd like to subclass int to support list access, treating the integer  
as if it were a list of bits.
Assigning bits to particular indices involves changing the value of  
the integer itself, but changing 'self' obviously just alters the  
value of that local variable.
Is there some way for me to change the value of the BitSequence  
object itself? I've also tried wrapping and delegating using  
__getattr__, but I couldn't figure out how to handle in-place methods.

Thanks for your help,
David Coffin


class BitSequence(int):
 """An integer emulating a sequence of bits, subclassing int."""
 def __new__(cls, value, length=32):
 inst = super(BitSequence,cls).__new__(cls, value)
 inst.length = length
 return inst

 def __setitem__(self, index, bit):
 mask = 1 << self.length - index - 1
 if bit == 1:
 # XXX only changing local 'self'
 self |= mask
 elif bit == 0:
 self &= ~mask

 def __getitem__(self, i):
 return (self >> (self.length - i -1)) & 1

 def __repr__(self):
 s = ''
 for i in xrange(self.length):
 s = str(self >> i & 1) + s
 return s + " : " + str(self)
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Re: changing value of 'self' when subclassing int

[David Coffin]

Thanks for all the help.

> On 20 Feb 2006, at 17:34, Alex Martelli wrote:
>
> ...integers are immutable, like all other numbers in Python: there  
> is NO
> way to "change the value of the integer itself".

So, on learning that I could subclass the number types, I didn't even  
consider the fact that they're immutable. I feel slightly foolish.  
And I'll look at gmpy straight away, it looks like it contains  
functionality I'll find useful.

> On 21 Feb 2006, at 10:58, Fuzzyman wrote:
>
> Probably your best bet is to have the assignment done as a method call
> which returns the new value.

I not sure that would be suitable in this case. I'm using genetic  
algorithm code containing some methods that assume 'individuals' are  
represented as bitstrings, and some that assume individuals are  
represented as lists of integers. Ideally, I could have created a  
class for the bitstring individuals that also supported list based  
bit assignment (without too much overhead).

Best wishes,
David Coffin
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Monkey patching new style classes

[David Coffin]

Is it possible to add an attribute to a new style class where the name of
that attribute is determined at runtime? In other words, is there an new
style class alternative to adding items to a classes __dict__ ?
Thanks.
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