On 2006-04-21, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
> Hello,
>
> I need your help understanding lambda (and doing it a better way
> without).
>
> f = lambda x : x*x
> [...]
> # the idea is now to give the definition of the multiplication of
> functions and integers
> # (f * c)(xx) := f(x)*c
> [lambda xx: f(xx)*y for y in range(1,5)][0](1)
> # returns 4
> # I would expect 1*x*x = 1
If you change the 5 in range(1,5) to a 10, this returns 9.
So it looks like each of the lambda xx : f(xx) * y is getting the last
value of y.
I can do this for example:
f = lambda x : x * x
fns = [lambda xx: f(xx)*y for y in range(1,10)]
for fn in fns:
print fn(1)
And I get 9 printed out 9 times.
It does seem a bit surprising, but I suppose if you think about it
there's only one "y"-- the one in the outer scope. This one variable is
bound 9 times, to a new value each time.
What one would need for it to work would be for each of the functions to
have a variable in its own scope. But you can't, as far as I know,
create local variables in functions defined with lambda.
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