a question about zip...

[KraftDiner]

I had a structure that looked like this
((0,1), (2, 3), (4, 5), (6,7)

I changed my code slightly and now I do this:
odd = (1,3,5,7)
even = (0,2,4,6)
all = zip(even, odd)

however the zip produces:
[(0, 1), (2, 3), (4, 5), (6, 7)]

Which is a list of tuples.. I wanted a tuple of tuples...

[Jan Niklas Fingerle]

Re: a question about zip...

KraftDiner <bobrien18@yaho o.com> wrote:[color=blue]
> [(0, 1), (2, 3), (4, 5), (6, 7)]
>
> Which is a list of tuples.. I wanted a tuple of tuples...[/color]
[color=blue][color=green][color=darkred]
>>> odd = (1,3,5,7)
>>> even = (0,2,4,6)
>>> all = zip(even, odd)
>>> all[/color][/color][/color]
[(0, 1), (2, 3), (4, 5), (6, 7)][color=blue][color=green][color=darkred]
>>> tuple(all)[/color][/color][/color]
((0, 1), (2, 3), (4, 5), (6, 7))

Cheers,
--Jan Niklas

[Xavier Morel]

Re: a question about zip...

KraftDiner wrote:[color=blue]
> I had a structure that looked like this
> ((0,1), (2, 3), (4, 5), (6,7)
>
> I changed my code slightly and now I do this:
> odd = (1,3,5,7)
> even = (0,2,4,6)
> all = zip(even, odd)
>
> however the zip produces:
> [(0, 1), (2, 3), (4, 5), (6, 7)]
>
> Which is a list of tuples.. I wanted a tuple of tuples...
>[/color]
tuple(zip(even, odd))

and if you fear for memory efficiency

tuple(iterator. izip(even, odd))

[Diez B. Roggisch]

Re: a question about zip...

KraftDiner schrieb:[color=blue]
> I had a structure that looked like this
> ((0,1), (2, 3), (4, 5), (6,7)
>
> I changed my code slightly and now I do this:
> odd = (1,3,5,7)
> even = (0,2,4,6)
> all = zip(even, odd)
>
> however the zip produces:
> [(0, 1), (2, 3), (4, 5), (6, 7)]
>
> Which is a list of tuples.. I wanted a tuple of tuples...[/color]

Use tuple(zip(...))

There is a reason that zip returns a list: appending to a list is considered a "natural" operation, whereas extending an
immutable(!) tuple creates a _new_ tuple for each entry. Which is a comparable costly operation - actually quadratic
complexity instead of linear.

So - if you need a tuple afterwards, convert it as shown above.

Diez

[Steven D'Aprano]

Re: a question about zip...

KraftDiner wrote:
[color=blue]
> I had a structure that looked like this
> ((0,1), (2, 3), (4, 5), (6,7)
>
> I changed my code slightly and now I do this:
> odd = (1,3,5,7)
> even = (0,2,4,6)
> all = zip(even, odd)
>
> however the zip produces:
> [(0, 1), (2, 3), (4, 5), (6, 7)]
>
> Which is a list of tuples.. I wanted a tuple of tuples...[/color]

Others have already told you how to do this. But I have
a question: why do you care that it is a tuple, not a
list? Is there something you need to do with it that
can be done with tuples but not lists?

In other words, while it isn't *wrong* to convert the
list to a tuple, perhaps it is *unnecessary*?


--
Steven.

[Steve Holden]

Re: a question about zip...

KraftDiner wrote:[color=blue]
> I had a structure that looked like this
> ((0,1), (2, 3), (4, 5), (6,7)
>
> I changed my code slightly and now I do this:
> odd = (1,3,5,7)
> even = (0,2,4,6)
> all = zip(even, odd)
>
> however the zip produces:
> [(0, 1), (2, 3), (4, 5), (6, 7)]
>
> Which is a list of tuples.. I wanted a tuple of tuples...
>[/color]
So apply tuple() to the list!

all = tuple(zip(even, odd))

regards
Steve
--
Steve Holden +44 150 684 7255 +1 800 494 3119
Holden Web LLC/Ltd www.holdenweb.com
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