python - Understanding the map function -

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map(function, iterable, ...)

apply function every item of iterable , return list of results. if additional iterable arguments passed, function must take many arguments , applied items iterables in parallel.

if 1 iterable shorter assumed extended none items.

if function none, identity function assumed; if there multiple arguments, map() returns list consisting of tuples containing corresponding items iterables (a kind of transpose operation).

the iterable arguments may sequence or iterable object; result list.

what role play in making cartesian product?

content = map(tuple, array)

what effect putting tuple anywhere in there have? noticed without map function output abc , it, it's a, b, c.

i want understand function. reference definitions hard understand. fancy fluff.

map isn't particularly pythonic. recommend using list comprehensions instead:

map(f, iterable)

is equivalent to:

[f(x) x in iterable]

map on own can't cartesian product, because length of output list same input list. can trivially cartesian product list comprehension though:

[(a, b) in iterable_a b in iterable_b]

the syntax little confusing -- that's equivalent to:

result = [] in iterable_a:     b in iterable_b:         result.append((a, b))

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