How do I make Maps and lambdas work with a matrix in python 3.4?

Question

I often avoid me to write posts like this but I\'m new in python 3.4 and I need a help with this code.

Suppose we have the following list:

v = [ [ x,         


        

Answer 1

I agree with Mike that map(lambda is silly. In this case, '{}{}'.format pretty much does the job your lambda is supposed to do, so you can use that instead:

starmap('{}{}'.format, v)

That uses itertools.starmap. If you want to use map, you can do it like this:

map('{}{}'.format, *zip(*v))

But really I'd just do

(c + str(n) for c, n in v)

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Edit: A comparison of map+lambda vs generator expression, showing that the latter is shorter, clearer, more flexible (unpacking), and faster:

>>> from timeit import timeit

>>> r = range(10000000)
>>> timeit(lambda: sum(map(lambda xy: xy[0]+xy[1], zip(r, r))), number=1)
7.221420832748007
>>> timeit(lambda: sum(x+y for x, y in zip(r, r)), number=1)
5.192609298897533

>>> timeit(lambda: sum(map(lambda x: 2*x, r)), number=1)
5.870139625224283
>>> timeit(lambda: sum(2*x for x in r), number=1)
4.4056527464802

>>> r = range(10)
>>> timeit(lambda: sum(map(lambda xy: xy[0]+xy[1], zip(r, r))), number=1000000)
7.047922363577214
>>> timeit(lambda: sum(x+y for x, y in zip(r, r)), number=1000000)
4.78059718055448