creating multiple generators from single loop

Question

So, consider the following:

iterable1 = (foo.value for foo in foos)
iterable2 = (bar.value(foo) for foo in foos)

Since both iterables are creates from same list.. I was wondering if I can generate them together..

like

compounded_iter = ( (foo.value,bar.value(foo)) for foo in foos)

The above works..

But is it possible to get something like:

iter1, iter2 = (......)  but in one shot?

I am not able to figure that out..

tckmn · Accepted Answer · 2014-12-17 22:54:45Z

6

compounded_iter = ( (foo.value,bar.value(foo)) for foo in foos)
iter1,iter2 = zip(*compounded_iter)

You can, of course, combine those into one line.

edited Dec 17, 2014 at 22:54

tckmn

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answered Dec 17, 2014 at 22:53

Joran Beasley

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5 Comments

Marcin Over a year ago

Is there something in itertools that can even make it simpler/easier?

Joran Beasley Over a year ago

@Marcin oh probably :P

frazman Over a year ago

@JoranBeasley: citer = ((1,2) for i in range(20) ) and then iter1,iter2 = zip(*citer) But iter1.next() throws error AttributeError: 'tuple' object has no attribute 'next'??

Ashwini Chaudhary Over a year ago

But due to the use of * you are not creating iterators here, this is going to consume all the data.

Joran Beasley Over a year ago

@AshwiniChaudhary yeah I know ...I cant really come up with a good way around it .... if i dont consume it then accessing either iter returned would consume the other also ...

TehTris · Accepted Answer · 2014-12-17 22:52:13Z

1

compounded_iter = ( (foo.value,bar.value(foo)) for foo in foos)
iter1,iter2 = [x[0] for x in compound_iter],[x[1] for x in compound_iter]

this would put all the values in iter1, and all the bar.values in iter2

answered Dec 17, 2014 at 22:52

TehTris

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3 Comments

tckmn Over a year ago

This isn't what the OP is asking—the question asked whether this can be done all at once (i.e. not in multiple lines).

frazman Over a year ago

I am trying to minimize the looping.. :( This has three for loops.. I am trying to get away with one.. :-/

Marcin Over a year ago

you still have twoseparate comprehensions here.

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