Steven D'Aprano wrote:
> I suppose someone might be able to come up with code that deliberately
> uses this feature for good use
argument binding is commonly used for optimization, and to give simple
functions persistent storage (e.g. memoization caches).
more importantly, it's the standard pydiom for passing object *values* (of
any kind) into an inner scope:
x = something
def myfunc(arg, x=x):
# myfunc needs the current value, not whatever x
# happens to be when the function is called
here's a typical gotcha:
for i in range(10):
def cb():
print "slot", i, "fired"
register_callback(slot=i, callback=cb)
to make this work as expected, you have to do
for i in range(10):
def cb(i=i):
print "slot", i, "fired"
register_callback(slot=i, callback=cb)
</F>
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