[Tutor] longest common substring
d at davea.name
Sun Nov 13 14:27:31 CET 2011
On 11/13/2011 08:06 AM, lina wrote:
> Finally, if I am not wrong again, I feel I am kinda of starting
> figuring out what's going on. Why it's None.
> The main mistake here I use result = result.append(something)
> the "="
> I checked the print(id(result)) and print(id(result.append()),
> For the NoneType they shared the same id 8823392 in my laptop. is it
> temporary address?
None is a unique object, deliberately. No matter how many times people
create None, it'll always be the same object. So
b = x.append(y)
a is b #(true)
id(a) == id(b) #(true)
Similarly True and False are unique objects.
Other objects which are equal to each other may or may not have the same
ID; you should not count on it. For example,
x = 45+3
y = 6*8
Checking (x==y) is true, of course. But checking (x is y) is
indeterminate. It may be true for the first ten tests you do, and false
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