side effects on *some* default parameters

[Duncan Booth]

Joe Grossberg <jgrossberg at matrixgroup.net> wrote in
news:mailman.1045154045.19349.python-list at python.org: 

> *Why* is this better than the alternative (i.e. default argument
> values get created every time the method/function is called without
> the parameter)? 
> 

Code like the following depends on the fact that the default argument 
values are only evaluated once when 'def' is executed, rather than when the 
function is called:

>>> adders = []
>>> for i in range(10):
	def addN(x, n=i): return x+n
	adders.append(addN)

	
>>> adders[4](3)
7

If the default argument was evaluated when the function was called, this 
would display 12 instead of 7. There would be no easy way to replicate the 
current behaviour if this were the case.


-- 
Duncan Booth                                             duncan at rcp.co.uk
int month(char *p){return(124864/((p[0]+p[1]-p[2]&0x1f)+1)%12)["\5\x8\3"
"\6\7\xb\1\x9\xa\2\0\4"];} // Who said my code was obscure?