[Python-Dev] second experiment

[Greg Wilson]

I'm giving a talk at the U. of Toronto tomorrow, and would like to re-run
the "what does it do?" experiment with list comprehensions and
simultaneous loops.  I propose asking the following:

The program:

    for x in [10, 20, 30]:
        print x

prints:

    10
    20
    30

and the program:

    for x in [10, 20, 30]:
        for y in [1, 2, 3]:
            print x+y

prints:

    11
    12
    13
    21
    22
    23
    31
    32
    33

Match each of the following:

(A) for x in [10, 20, 30]; y in [1, 2, 3]:
        print x+y

(B) for (x,y) in zip([10, 20, 30], [1, 2, 3]):
        print x+y

(C) for (x in [10, 20, 30]) and (y in [1, 2, 3]):
        print x+y

(D) something else

to their output:

(1) 11
    22
    33

(2) 11
    12
    13
    21
    22
    23
    31
    32
    33

(3) "Run-Time Error"

Questions:

1. What should option (D) be?

2. Should the lists be the same length, or different lengths?  I think the
   latter is the trickier case (equally reasonable to say "iterate for
   length of shortest" and "error if lists' lengths unequal") --- is that
   worth testing?

3. Can someone provide a couple of list comprehension alternatives as
   well?

Reactions?

Greg