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From: Peter Otten on 16 Dec 2009 10:42
Tobias Weber wrote:

> how do I subclass or at least add a method to something returned by
> re.compile()?

Let's see:

>>> import re
>>> r = re.compile("yadda")
>>> class S(type(r)): pass
....
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: Error when calling the metaclass bases
type '_sre.SRE_Pattern' is not an acceptable base type

So I'm afraid you can't subclass...

>>> def hello(self): print "hello"
....
>>> type(r).hello = hello
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: can't set attributes of built-in/extension type
'_sre.SRE_Pattern'
>>> r.hello = hello
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: '_sre.SRE_Pattern' object has no attribute 'hello'

....nor add a method...

>>> class W(object):
.... def __init__(self, match):
.... self._match = match
.... def __getattr__(self, name):
.... return getattr(self._match, name)
.... hello = hello
....
>>> def my_compile(*args, **kw):
.... m = original_compile(*args, **kw)
.... if m is not None:
.... return W(m)
....
>>> original_compile = re.compile
>>> re.compile = my_compile
>>> re.compile("yadda").hello()
hello

....but alter the meaning of "something returned by re.compile()" you can.
Now who would want to do that? And why?

Peter
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