Question

problem:
when you use construction

for a in _list_:
    print a

it prints every item in array. But you can’t alter array. Is it possible to alter value of array (something like a=123, but that ain’t working)
I know it’s possible (for example in while loop), but I want to do it this way (more elegant)

In PHP it would be like

foreach ($array as &$value) {
    $value = 123;
}

(because of & sign, is passed as reference)

Answer 1

for idx, a in enumerate(foo):
    foo[idx] = a + 42

Note though, that if you’re doing this, you probably should look into list comprehensions (or map), unless you really want to mutate in place (just don’t insert or remove items from iterated-on list).

The same loop written as a list comprehension looks like:

foo = [a + 42 for a in foo]