I can’t find imap() in itertools in Python 3
itertools.imap() is in Python 2, but not in Python 3. Actually, that function was moved to just the map function in Python 3 and if you want to use the old Python 2 map, you must use list(map()).
iterator
Why do we need to use iterator on ArrayList in Java? [duplicate]
As you have stated iterator is used when you want to remove stuff whilst you iterate over the array contents. If you don’t use an iterator but simply have a for loop and inside it use the remove method you will get exceptions because the contents of the array changes while you iterate through. e.g: … Read more
Iterating over a slice’s values instead of references in Rust?
You can remove the reference by destructuring in the pattern: // | // v for &var in slice { other_fn(var); } However, this only works for Copy-types! If you have a type that doesn’t implement Copy but does implement Clone, you could use the cloned() iterator adapter; see Chris Emerson’s answer for more information.
An elegant and fast way to consecutively iterate over two or more containers in Python?
Depending on what order you want to process the items: import itertools for items in itertools.izip(deque1, deque2, deque3): for item in items: some_action(item) for item in itertools.chain(deque1, deque2, deque3): some_action(item) I’d recommend doing this to avoid hard-coding the actual deques or number of deques: deques = [deque1, deque2, deque3] for item in itertools.chain(*deques): some_action(item) To … Read more
What is the simplest way to create an empty iterable using yield in Python?
Yes, there is: return iter([])
How can std::vector access elements with huge gaps between them?
You’ve been fooled. The iterator returned by std::back_inserter has it++ as a no-op. So those ‘gaps’ you are creating? Yeah that’s all doing nothing.
Why do iterators need to be default-constructible
Forward iterators and stronger are required to refer to some external sequence (see [forward.iterators]/6 which says “If a and b are both dereferenceable, then a == b if and only if *a and *b are bound to the same object.”) This means they are generally just a lightweight handle onto something else (e.g. a pointer … Read more
What characters are grouped with Array.from?
Array.from first tries to invoke the iterator of the argument if it has one, and strings do have iterators, so it invokes String.prototype[Symbol.iterator], so let’s look up how the prototype method works. It’s described in the specification here: Let O be ? RequireObjectCoercible(this value). Let S be ? ToString(O). Return CreateStringIterator(S). Looking up CreateStringIterator eventually … Read more
comparing iterators from different containers
If you consider the C++11 standard (n3337): § 24.2.1 — [iterator.requirements.general#6] An iterator j is called reachable from an iterator i if and only if there is a finite sequence of applications of the expression ++i that makes i == j. If j is reachable from i, they refer to elements of the same sequence. … Read more
Detect last iteration in FOR OF loop in ES6 javascript
One approach is using Array.prototype.entries(): for (const [i, value] of arr.entries()) { if (i === arr.length – 1) { // do your thing } } Another way is keeping a count outside the loop like Shidersz suggested. I don’t think you want to check indexOf(item) though because that poses a problem if the last item … Read more