for in loops over enumerable property names of an object. for of (new in ES6) does use an object-specific iterator and loops over the values generated by that. In your example, the array iterator does yield all the values in the array (ignoring non-index properties).
You’re modifying the list while you iterate over it. That means that the first time through the loop, i == 1, so 1 is removed from the list. Then the for loop goes to the second item in the list, which is not 2, but 3! Then that’s removed from the list, and then the … Read more
The comma operator evaluates all its operands and yields the value of the last one. So basically whichever condition you write first, it will be disregarded, and the second one will be significant only. for (i = 0; j >= 0, i <= 5; i++) is thus equivalent with for (i = 0; i <= … Read more
For most purposes, you probably won’t notice a difference. However, foreach reads each line into a list (not an array) before going through it line by line, whereas while reads one line at a time. As foreach will use more memory and require processing time upfront, it is generally recommended to use while to iterate … Read more
You can also do it with recursion: def reverse(text): if len(text) <= 1: return text return reverse(text[1:]) + text[0] And a simple example for the string hello: reverse(hello) = reverse(ello) + h # The recursive step = reverse(llo) + e + h = reverse(lo) + l + e + h = reverse(o) + l + … Read more
You can use random.shuffle() to, well, shuffle a list: import random r = list(range(1000)) random.shuffle(r) for i in r: # do something with i By the way, in many cases where you’d use a for loop over a range of integers in other programming languages, you can directly describe the “thing” you want to iterate … Read more
You can achieve desired outcome from the other end by making the prototype methods not enumerable: Object.defineProperty(Array.prototype, “containsKey”, { enumerable: false, value: function(obj) { for(var key in this) if (key == obj) return true; return false; } }); This usually works better if you have control over method definitions, and in particular if you have … Read more
but on the other hand it creates a completely useless list of integers just to loop over them. Isn’t it a waste of memory, especially as far as big numbers of iterations are concerned? That is what xrange(n) is for. It avoids creating a list of numbers, and instead just provides an iterator object. In … Read more
How about: for (unsigned i = n ; i– > 0 ; ) { // do stuff with i }