Questions tagged [for-loop]
A for loop is a control structure used by many programming languages to iterate over a range. It is a way of repeating statements a number of times until the loop ends. Depending on the language this may be over a range of integers, iterators, etc.
for-loop
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Loop through an array in JavaScript
In Java, you can use a for loop to traverse objects in an array as follows:
String[] myStringArray = {"Hello", "World"};
for (String s : myStringArray) {
// Do something
}
Can ...
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How do I loop through or enumerate a JavaScript object?
I have a JavaScript object like the following:
var p = {
"p1": "value1",
"p2": "value2",
"p3": "value3"
};
How do I loop ...
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Why is printing "B" dramatically slower than printing "#"?
I generated two matrices of 1000 x 1000:
First Matrix: O and #.
Second Matrix: O and B.
Using the following code, the first matrix took 8.52 seconds to complete:
Random r = new Random();
for (int i = ...
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How do I iterate over a range of numbers defined by variables in Bash?
How do I iterate over a range of numbers in Bash when the range is given by a variable?
I know I can do this (called "sequence expression" in the Bash documentation):
for i in {1..5}; do ...
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Why is using "for...in" for array iteration a bad idea?
I've been told not to use for...in with arrays in JavaScript. Why not?
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How do I iterate through two lists in parallel?
I have two iterables, and I want to go over them in pairs:
foo = [1, 2, 3]
bar = [4, 5, 6]
for (f, b) in iterate_together(foo, bar):
print("f:", f, " | b:", b)
That should ...
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Difference between ( for... in ) and ( for... of ) statements?
I know what is a for... in loop (it iterates over the keys), but I have heard about for... of for the first time (it iterates over values).
I am confused about for... of loop.
var arr = [3, 5, 7];
arr....
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What is the difference between ++i and i++?
In C, what is the difference between using ++i and i++, and which should be used in the incrementation block of a for loop?
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A for-loop to iterate over an enum in Java
I have an enum in Java for the cardinal and intermediate directions:
public enum Direction {
NORTH,
NORTHEAST,
EAST,
SOUTHEAST,
SOUTH,
SOUTHWEST,
WEST,
NORTHWEST
}
How can I ...
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How to loop over files in directory and change path and add suffix to filename
I need to write a script that starts my program with different arguments. I start my program with:
./MyProgram.exe Data/data1.txt [Logs/data1_Log.txt].
Here is the pseudocode for what I want to do:
...
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Why does python use 'else' after for and while loops?
I understand how this construct works:
for i in range(10):
print(i)
if i == 9:
print("Too big - I'm giving up!")
break
else:
print("Completed successfully&...
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Get loop counter/index using for…of syntax in JavaScript
I understand that the basic for...of syntax in JavaScript looks like this:
for (let obj of myArray) {
// ...
}
But how do I get the loop counter/index when iterating with this syntax?
(With the ...
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Java 8 Iterable.forEach() vs foreach loop
Which of the following is better practice in Java 8?
Java 8:
joins.forEach(join -> mIrc.join(mSession, join));
Java 7:
for (String join : joins) {
mIrc.join(mSession, join);
}
I have lots ...
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How do you loop through a std::map?
I want to iterate through each element in the map<string, int> without knowing any of its string-int values or keys.
What I have so far:
void output(map<string, int> table)
{
map&...
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Iterate all files in a directory using a 'for' loop
How can I iterate over each file in a directory using a for loop?
And how could I tell if a certain entry is a directory or if it's just a file?
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answers
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In .NET, which loop runs faster, 'for' or 'foreach'?
In C#/VB.NET/.NET, which loop runs faster, for or foreach?
Ever since I read that a for loop works faster than a foreach loop a long time ago I assumed it stood true for all collections, generic ...
423
votes
24
answers
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views
Can I use break to exit multiple nested 'for' loops?
Is it possible to use the break function to exit several nested for loops?
If so, how would you go about doing this? Can you also control how many loops the break exits?
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Why does the order of the loops affect performance when iterating over a 2D array?
Below are two programs that are almost identical except that I switched the i and j variables around. They both run in different amounts of time. Could someone explain why this happens?
Version 1
#...
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How to use range-based for() loop with std::map?
The common example for C++11 range-based for() loops is always something simple like this:
std::vector<int> numbers = { 1, 2, 3, 4, 5, 6, 7 };
for ( auto xyz : numbers )
{
std::cout <&...
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What is the most efficient way to loop through dataframes with pandas?
I want to perform my own complex operations on financial data in dataframes in a sequential manner.
For example I am using the following MSFT CSV file taken from Yahoo Finance:
Date,Open,High,Low,...
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Pythonic way to combine for-loop and if-statement
I know how to use both for loops and if statements on separate lines, such as:
>>> a = [2,3,4,5,6,7,8,9,0]
... xyz = [0,12,4,6,242,7,9]
... for x in xyz:
... if x in a:
... print(...
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Django - iterate number in for loop of a template
I have the following for loop in my django template displaying days. I wonder, whether it's possible to iterate a number (in the below case i) in a loop. Or do I have to store it in the database and ...
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How to get the selected radio button’s value? [duplicate]
I’m having some strange problem with my JS program. I had this working properly but for some reason it’s no longer working. I just want to find the value of the radio button (which one is selected) ...
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How to get the current index in for each Kotlin
How to get the index in a for each loop? I want to print numbers for every second iteration
For example
for (value in collection) {
if (iteration_no % 2) {
//do something
}
}
In java, ...
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361
votes
3
answers
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Get loop count inside a for-loop [duplicate]
This for loop iterates over all elements in a list:
for item in my_list:
print item
Is there a way to know within the loop how many times I've been looping so far? For instance, I want to take a ...
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Difference between pre-increment and post-increment in a loop?
Is there a difference in ++i and i++ in a for loop? Is it simply a syntax thing?
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Is there a way to access an iteration-counter in Java's for-each loop?
Is there a way in Java's for-each loop
for(String s : stringArray) {
doSomethingWith(s);
}
to find out how often the loop has already been processed?
Aside from using the old and well-known for(...
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How to make my custom type to work with "range-based for loops"?
Like many people these days I have been trying the different features that C++11 brings. One of my favorites is the "range-based for loops".
I understand that:
for(Type& v : a) { ... }
Is ...
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Is it possible to declare two variables of different types in a for loop?
Is it possible to declare two variables of different types in the initialization body of a for loop in C++?
For example:
for(int i=0,j=0 ...
defines two integers. Can I define an int and a char in ...
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What is the pythonic way to detect the last element in a 'for' loop?
How can I treat the last element of the input specially, when iterating with a for loop? In particular, if there is code that should only occur "between" elements (and not "after" ...
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How do I break out of a loop in Scala?
How do I break out a loop?
var largest=0
for(i<-999 to 1 by -1) {
for (j<-i to 1 by -1) {
val product=i*j
if (largest>product)
// I want to break out here
...
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How to check if all elements of a list match a condition?
I have a list that contains many sub-lists of 3 elements each, like:
my_list = [["a", "b", 0], ["c", "d", 0], ["e", "f", 0], .....]
The ...
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How do I loop through a list by twos? [duplicate]
I want to loop through a Python list and process 2 list items at a time. Something like this in another language:
for(int i = 0; i < list.length(); i+=2)
{
// do something with list[i] and list[...
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Are loops really faster in reverse?
I've heard this quite a few times. Are JavaScript loops really faster when counting backward? If so, why? I've seen a few test suite examples showing that reversed loops are quicker, but I can't find ...
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Iterate through a C++ Vector using a 'for' loop
I am new to the C++ language. I have been starting to use vectors, and have noticed that in all of the code I see to iterate though a vector via indices, the first parameter of the for loop is always ...
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Check if object value exists within a Javascript array of objects and if not add a new object to array
If I have the following array of objects:
[ { id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 2, username: 'ted' } ]
Is there a way to loop through the array to check whether a ...
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Why use iterators instead of array indices?
Take the following two lines of code:
for (int i = 0; i < some_vector.size(); i++)
{
//do stuff
}
And this:
for (some_iterator = some_vector.begin(); some_iterator != some_vector.end();
...
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How do I annotate types in a for-loop?
I want to annotate a type of a variable in a for-loop. I tried this but it didn't work:
for i: int in range(5):
pass
What I expect is working autocomplete in PyCharm 2016.3.2, but using
pre-...
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How to use continue in jQuery each() loop?
In my application i am using AJAX call. I want to use break and continue in this jQuery loop.
$('.submit').filter(':checked').each(function() {
});
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TypeScript for ... of with index / key?
As described here TypeScript introduces a foreach loop:
var someArray = [9, 2, 5];
for (var item of someArray) {
console.log(item); // 9,2,5
}
But isn't there any index/key? I would expect ...
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Post-increment and pre-increment within a 'for' loop produce same output [duplicate]
The following for loops produce identical results even though one uses post increment and the other pre-increment.
Here is the code:
for(i=0; i<5; i++) {
printf("%d", i);
}
for(i=0; i<5; +...
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Breaking out of a nested loop
If I have a for loop which is nested within another, how can I efficiently come out of both loops (inner and outer) in the quickest possible way?
I don't want to have to use a boolean and then have ...
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Is it possible to make a `for` loop without an iterator variable? (How can I make code loop a set number of times?)
Is it possible to do following without the i?
for i in range(some_number):
# do something
If you just want to do something N amount of times and don't need the iterator.
238
votes
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GoTo Next Iteration in For Loop in java
Is there a token in java that skips the rest of the for loop?
Something like VB's Continue in java.
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How can I loop through a List<T> and grab each item?
How can I loop through a List and grab each item?
I want the output to look like this:
Console.WriteLine("amount is {0}, and type is {1}", myMoney.amount, myMoney.type);
Here is my code:
static ...
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Are list-comprehensions and functional functions faster than "for loops"?
In terms of performance in Python, is a list-comprehension, or functions like map(), filter() and reduce() faster than a for loop? Why, technically, they run in a C speed, while the for loop runs in ...
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How to add leading zeros for for-loop in shell? [duplicate]
I have a basic number for loop which increments the variable num by 1 over each iteration...
for (( num=1; num<=5; num++ ))
do
echo $num
done
Which outputs:
1
2
3
4
5
I'm trying to make it ...
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Elements order in a "for (… in …)" loop
Does the "for…in" loop in Javascript loop through the hashtables/elements in the order they are declared? Is there a browser which doesn't do it in order?
The object I wish to use will be declared ...
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How to efficiently remove all null elements from a ArrayList or String Array?
I try with a loop like that
// ArrayList tourists
for (Tourist t : tourists) {
if (t != null) {
t.setId(idForm);
}
}
But it isn't nice. Can anyone suggest me a better ...
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