[Python-Dev] re: list comprehension / pop quiz

[Greg Wilson]

I sent the message below to the 11 developers here in the office this
morning.  They all have 10+ years experience with C, and 2-3 years with
C++, Java, or both.  None have used Python (I'm working on it :-), but two
have extensive Perl experience, and one worked on and with functional
languages in grad school.  The question was:

    OK, folks, language question.  Given the statement:

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

    (note that the second list is shorter than the first), would you
    expect to see:

    (A) 'x' and 'y' move forward at the same rate:

        11
        22

    (B) 'y' goes through the second list once for each value of 'x':

        11
        12
        21
        22
        31
        32

    (C) an error message because the two lists are not the same length?

    Votes to me, please.

    Thanks,
    Greg

*Everyone* voted (B).  As useful as this capability is, I therefore think
the proposed syntax is likely to mislead.

Hope it's helpful,
Greg