Try this: [(i, j) for i, j in enumerate(mylist)] You need to put i,j inside a tuple for the list comprehension to work. Alternatively, given that enumerate() already returns a tuple, you can return it directly without unpacking it first: [pair for pair in enumerate(mylist)] Either way, the result that gets returned is as expected: … Read more
You still need to check if (items != null) otherwise you will get NullReferenceException. However you can do something like this: List<string> items = null; foreach (var item in items ?? new List<string>()) { item.Dump(); } but you might check performance of it. So I still prefer having if (items != null) first. Based on … Read more
I have an answer based on Iterating over a Tuple: #include <tuple> #include <utility> #include <iostream> template<std::size_t I = 0, typename… Tp> inline typename std::enable_if<I == sizeof…(Tp), void>::type print(std::tuple<Tp…>& t) { } template<std::size_t I = 0, typename… Tp> inline typename std::enable_if<I < sizeof…(Tp), void>::type print(std::tuple<Tp…>& t) { std::cout << std::get<I>(t) << std::endl; print<I + 1, … Read more
TL;DR Your best bets are usually a for-of loop (ES2015+ only; spec | MDN) – simple and async-friendly for (const element of theArray) { // …use `element`… } forEach (ES5+ only; spec | MDN) (or its relatives some and such) – not async-friendly (but see details) theArray.forEach(element => { // …use `element`… }); a simple … Read more
TLDR; No, for loops are not blanket “bad”, at least, not always. It is probably more accurate to say that some vectorized operations are slower than iterating, versus saying that iteration is faster than some vectorized operations. Knowing when and why is key to getting the most performance out of your code. In a nutshell, … Read more
Loop over the file to read lines: with open(‘somefile’) as openfileobject: for line in openfileobject: do_something() File objects are iterable and yield lines until EOF. Using the file object as an iterable uses a buffer to ensure performant reads. You can do the same with the stdin (no need to use raw_input(): import sys for … Read more
This is as pythonic as you can get: for lat, long in zip(Latitudes, Longitudes): print(lat, long)
Beware of properties inherited from the object’s prototype (which could happen if you’re including any libraries on your page, such as older versions of Prototype). You can check for this by using the object’s hasOwnProperty() method. This is generally a good idea when using for…in loops: var user = {}; function setUsers(data) { for (var … Read more
Here’s a way to do it by making use of the way adding one day causes the date to roll over to the next month if necessary, and without messing around with milliseconds. Daylight savings aren’t an issue either. var now = new Date(); var daysOfYear = []; for (var d = new Date(2012, 0, … Read more
Well, you could do something like this using Java 8’s time-API, for this problem specifically java.time.LocalDate (or the equivalent Joda Time classes for Java 7 and older) for (LocalDate date = startDate; date.isBefore(endDate); date = date.plusDays(1)) { … } I would thoroughly recommend using java.time (or Joda Time) over the built-in Date/Calendar classes.