However, is there a good reason why default parameters aren't evaluated as the function is called? (apart from efficiency and backwards compatibility)?
So, one of my really common use cases that takes advantage of the fact that default parameters are evaluated at function definition time:
def foo(bar, baz, matcher=re.compile(r'...')):
...
text = matcher.sub(r'...', text)
...If default parameters were evaluated when the function was called, my regular expression would get re-compiled every time foo() was called. This would be inefficient, especially if foo() got called a lot. If Python 3000 changed the evaluation time of default parameters, I could rewrite this code as:
class foo(object):
matcher=re.compile(r'...')
def __new__(self, bar, baz, matcher=None):
if matcher is None:
matcher = self.matcher
...
text = matcher.sub(r'...', text)
...But that seems like a lot of work to do something that used to be pretty simple...
Steve -- http://mail.python.org/mailman/listinfo/python-list
