Dictionaries, popitem() method example

[Steve Holden]

"Antonios B. Kaklis" <antoni3 at otenet.gr> wrote ...
> Hello to everybody...'

Hello

> There is something that i' don't understand.
> In the Python Library Reference, Section 2.1.6 "Mapping Types"
> It says: "a.popitem( )" --->Note 6: Is useful to destructively iterate
over
>                                                      a dictionary as often
> used in set algorithms!
>
> I don't understand  1) what is "Destructively iteration over a dictionary"

This simply means that the item returned by popitem() no longer exists in
the dictionary. So if you popitem() enough you will have destryoed it (left
it empty - it's still a dictionary)!

>                              2) Set Algotithms

Algorithms that treat the items in the dictionary as a set! The dictionary
is a natural structure for this since the presence of an item under a
particular key is easily detected, and a key is either present or not.

regards
 Steve
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