object identity and hashing

[castironpi@gmail.com]

Can someone explain this?

>>a= {}
>>a[(3,)]= 0
>>(3,) in a

True

>>(3,) is (3,)

False

[Jeff Schwab]

Re: object identity and hashing

castironpi@gmai l.com wrote:

Can someone explain this?
>

>>>a= {}

Create an empty dict and bind it to the name a.

>>>a[(3,)]= 0

Set the key/value pair (3,):0 to the dict.

>>>(3,) in a

Is (3,) one of the keys in the dict?

True

Yes, it is.

>>>(3,) is (3,)

Create two separate tuples (that happen to be equivalent). Are they the
same object?

False

No, they are not.

Every time you write (3,), you are potentially creating a new object.
These objects have equal values (and hash codes), so they are
interchangeable for purposes of keying a dict.

[castironpi@gmail.com]

Re: object identity and hashing

On Feb 24, 7:58 pm, Jeff Schwab <j...@schwabcen ter.comwrote:

castiro...@gmai l.com wrote:

Can someone explain this?

>

>>a= {}

>
Create an empty dict and bind it to the name a.
>

>>a[(3,)]= 0

>
Set the key/value pair (3,):0 to the dict.
>

>>(3,) in a

>
Is (3,) one of the keys in the dict?
>

True

>
Yes, it is.
>

>>(3,) is (3,)

>
Create two separate tuples (that happen to be equivalent).  Are they the
same object?
>

False

>
No, they are not.
>
Every time you write (3,), you are potentially creating a new object.
These objects have equal values (and hash codes), so they are
interchangeable for purposes of keying a dict.

I see. You stated,

Is (3,) one of the keys in the dict?
>

True

>
Yes, it is.

It isn't, but it does equal a key that's already in the dict.