a Python bug in processing __del__ method ??

[Baoqiu Cui]

Today I was playing with a small Python program using Python 2.4
on Cygwin (up-to-date version, on Windows XP), but ran into a
strange error on the following small program (named bug.py):

---
#!/usr/bin/python

class Person:
population = 0
def __del__(self):
Person.population -= 1

peter = Person()
---

The error returned is this:

$ python bug.py
Exception exceptions.AttributeError: "'NoneType' object has no
attribute 'population'" in > ignored

However, if I rename variable name 'peter' to something like 'peter1'
or 'david', the error is gone.  Looks to me the
error only happens to variable name 'peter'.

Does anyone know what is wrong?  Is this a bug only on Cygwin?
- Baoqiu

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Re: a Python bug in processing __del__ method ??

[Baoqiu Cui]

Fredrik and Steve,

Thank you so much for the help.  Now I know more about Python. :-)

Steve's test does explain why 'peter1' is OK while 'peter' is not:
'peter1' appears
before 'Person' in the globals while 'peter' is after.

The error message is just a little confusing to a Python newbie, I
think.

Thanks again!

- Baoqiu

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Re: deleting texts between patterns

[Baoqiu Cui]

John Machin <[EMAIL PROTECTED]> writes:

> Uh-oh.
>
> Try this:
>
>>>> pat = re.compile('(?<=abc\n).*?(?=xyz\n)', re.DOTALL)
>>>> re.sub(pat, '', linestr)
> 'blahfubarabc\nxyz\nxyzzy'

This regexp still has a problem.  It may remove the lines between two
lines like 'aaabc' and 'xxxyz' (and also removes the first two 'x's in
'xxxyz').

The following regexp works better:

  pattern = re.compile('(?<=^abc\n).*?(?=^xyz\n)', re.DOTALL | re.MULTILINE)

>>> lines = '''line1
... abc
... line2
... xyz
... line3
... aaabc
... line4
... xxxyz
... line5'''
>>> pattern = re.compile('(?<=^abc\n).*?(?=^xyz\n)', re.DOTALL | re.MULTILINE)
>>> print pattern.sub('', lines)
line1
abc
xyz
line3
aaabc
line4
xxxyz
line5
>>> 

- Baoqiu

-- 
Baoqiu Cui 
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