On 9/27/2011 6:32 PM, Guido van Rossum wrote:
On Tue, Sep 27, 2011 at 3:24 PM, Arnaud Delobelle<arnodel@gmail.com> wrote:
I may be unduly worrying about this, but it feels to me that it lessens the overall tidiness of the language. I would much rather there was a way to initialise these "own" variables outside the body of the function.
Yes, you have a point. Hiding side effects this way could be nasty, and this is actually the first point in favor of the default argument hack I've heard in a while. :-)
I have several times written on python-list that Python has a simple rule: header expressions (for default args) are evaluated one-time when the function is defined; body expressions are evaluated (perhaps) each time when the function is called. If people understand this and do not fight it, they are not surprised that mutating a once-defined default arg mutates it, nor that defining a function inside a loop magically causes define-time binding of names in the body. I would hate for Python to lose this simplicity. I consider it one of its positive features. -- Terry Jan Reedy