Without else, code block will run after the loop terminates, no matter what. Here, one might think, “Why not put the code in code block immediately after the loop? Won’t it accomplish the same thing?” This piece of code prints out integers between 0 and 9. This process will repeat until the condition becomes false. If it is true, the code in loop body is executed. In a while loop, the condition is first checked. With the while loop, we can execute a block of code as long as a condition is true. This snippet of code will use a condition to get the list of even numbers between 0 and 9: Notice that in this case, we don’t have a conditional statement. We can use the range method in list comprehension like so: numbers = According to our condition, all elements containing the letter B will be added to the namesWithB list. In this code, we iterated through the names array. Let’s rewrite our code that we wrote earlier using list comprehension: names = The elements of list will be appended to the newlist array if loop variable fulfills the condition. Here, expression can be a piece of code that returns a value, for example, a method. Using the power of list comprehension, we can shrink this block of code by a large extent. If true, the program appends this corresponding element to the namesWithB list. In this code, we used the for command to iterate through the names array and then checked whether any element contains the letter B. NamesWithB.append(name) # add this element to this array. In some cases, you might want to create a new list based off the data of an existing list.įor example, look at the following code: names = If "B" in name: # does the name include 'B'? The snippet below uses an if statement to return all the names that include letter ‘B’: names = # create our list Later on, we used the for command to iterate through the names array and then logged out the contents of this list. In the above snippet, we created a list called names. We can even use a for loop to iterate through lists: names = # create our listįor name in names: # load our list of names and iterate through them Discover popular ORMs used in the TypeScript landscape.Explore Tauri, a new framework for building binaries.Learn how to animate your React app with AnimXYZ.Switch between multiple versions of Node.Use React's useEffect to optimize your application's performance.Don't miss a moment with The Replay, a curated newsletter from LogRocket.The code within loop body keeps on running until i reaches the end of the collection. The loop variable, i, takes on the value of the next element in collection each time through the loop. It also has the ability to iterate over the items of any sequence, such as a list or a string. In this article, you will learn the following concepts:Ī for loop is a type of loop that runs for a preset number of times. while: Keep on iterating until the condition is false.This is also known as a definite iteration for: Iterate a predefined number of times.In Python, there are two kinds of loop structures: As a result, this saves time and promotes code readability. To summarize, developers use loops to run a piece of code multiple times until a certain condition is met. We will learn about while loops later in this article. If this condition is satisfied, the program keeps on running the eat_food function until the condition becomes false. Here, the loop first analyzes whether the stomach_empty Boolean is true. In this code, we are using a while statement. To mitigate this problem, we can use a loop structure like so: WHILE stomach_empty //this code will keep on running if stomach_empty is true Furthermore, notice that we are typing the same code multiple times, which means that this breaks the DRY rule of programming. If this condition is met, the program will execute the eat_food method. Here, we are checking whether the stomach_empty variable is true. This code will keep on running unless the condition becomes invalid.įor example, look at the following block of pseudo code: IF stomach_empty If this condition is true, some piece of code is run. In a loop structure, the program first checks for a condition. Loops are an essential construct in all programming languages. Octo6 min read 1896 What are loops and when do you use them? Hussain Arif Follow Hussain is a CS student in Pakistan whose biggest interest is learning and teaching programming to make the world a better place.
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