For the specific question of generating a reverse IntStream, try something like this: static IntStream revRange(int from, int to) { return IntStream.range(from, to) .map(i -> to – i + from – 1); } This avoids boxing and sorting. For the general question of how to reverse a stream of any type, I don’t know of … Read more
The effects of the three different methods to remove an element from a list: remove removes the first matching value, not a specific index: >>> a = [0, 2, 3, 2] >>> a.remove(2) >>> a [0, 3, 2] del removes the item at a specific index: >>> a = [9, 8, 7, 6] >>> del … Read more
In terms of speed, it’s no competition for empty lists/dicts: >>> from timeit import timeit >>> timeit(“[]”) 0.040084982867934334 >>> timeit(“list()”) 0.17704233359267718 >>> timeit(“{}”) 0.033620194745424214 >>> timeit(“dict()”) 0.1821558326547077 and for non-empty: >>> timeit(“[1,2,3]”) 0.24316302770330367 >>> timeit(“list((1,2,3))”) 0.44744206316727286 >>> timeit(“list(foo)”, setup=”foo=(1,2,3)”) 0.446036018543964 >>> timeit(“{‘a’:1, ‘b’:2, ‘c’:3}”) 0.20868602015059423 >>> timeit(“dict(a=1, b=2, c=3)”) 0.47635635255323905 >>> timeit(“dict(bar)”, setup=”bar=[(‘a’, 1), (‘b’, … Read more
Given li in the question: li = list(zip(range(1, 14), range(14, 27))) To unpack the data from pairs into lists use zip: x, y = zip(*li) x → (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13) y → (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26) … Read more
You could use a list comprehension or a generator expression instead: ‘, ‘.join([str(x) for x in list]) # list comprehension ‘, ‘.join(str(x) for x in list) # generator expression
>>> xs = list(range(165)) >>> xs[0::10] [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160] Note that this is around 100 times faster than looping and checking a modulus for each element: $ python -m timeit -s “xs = list(range(1000))” “[x for i, x in enumerate(xs) if … Read more
Like this: keys = [‘a’, ‘b’, ‘c’] values = [1, 2, 3] dictionary = dict(zip(keys, values)) print(dictionary) # {‘a’: 1, ‘b’: 2, ‘c’: 3} Voila 🙂 The pairwise dict constructor and zip function are awesomely useful.
>>> [“foo”, “bar”, “baz”].index(“bar”) 1 See the documentation for the built-in .index() method of the list: list.index(x[, start[, end]]) Return zero-based index in the list of the first item whose value is equal to x. Raises a ValueError if there is no such item. The optional arguments start and end are interpreted as in the … Read more
Use the built-in function enumerate(): for idx, x in enumerate(xs): print(idx, x) It is non-pythonic to manually index via for i in range(len(xs)): x = xs[i] or manually manage an additional state variable. Check out PEP 279 for more.
fun foo(vararg strings: String) { /*…*/ } Using foo(strings = arrayOf(“a”, “b”, “c”)) val list: MutableList<String> = listOf(“a”, “b”, “c”) as MutableList<String> foo(strings = list.map { it }.toTypedArray()) Named arguments are not allowed for non-Kotlin functions (*.java) So, in this case you should replace: From: strings = list.map { it }.toTypedArray() To: *list.map { it … Read more