Ben C escribió:
> On 2006-04-21, Ben C <[EMAIL PROTECTED]> wrote:
> Having said that, I attempted to confirm this using def rather than
> lambda, and encountered something I cannot explain at all-- it appears
> that the functions are getting redefined whenever they are called, to
> effect a kind of "dynamic scoping" behaviour. I would appreciate any
> explanation anyone can give of this:
>
> fns = []
> for y in range(2):
> def fn():
> yy = y # exactly the same with yy = int(y)
> print "defining fn that returns", yy
> return yy
> print "Appending at", y
> print fn, fn()
> fns.append(fn)
yy = y does assign y's current value (current == fn call time, not fn
definition time). To return 0 and 1 as expected you should create a
"different/private" y for every fn's definition.
----------------------------------------
fns = []
for y in range(2):
def fn(y=y):
yy = y
print "defining fn that returns", yy
return yy
print "Appending at", y
print fn, fn()
fns.append(fn)
----------------------------------------
fns = []
def factory(y) :
def fn() :
yy = y
print "defining fn that returns", yy
return yy
return fn
for y in range(2) :
fn = factory(y)
print "Appending at", y
print fn, fn()
fns.append(fn)
----------------------------------------
HTH
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