How to restart a while loop in python

With the while loop we can execute a set of statements as long as a condition is true. The while loop requires relevant variables to be ready, in this example we need to define an indexing variable, iwhich we set to 1. With the break statement we can stop the loop even if the while condition is true:. With the continue statement we can stop the current iteration, and continue with the next:.

how to restart a while loop in python

With the else statement we can run a block of code once when the condition no longer is true:. Print i as long as i is less than 6. If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail:.

Note: remember to increment i, or else the loop will continue forever. Exercise: Print i as long as i is less than 6. HOW TO.

Restarting a Python Script Within Itself

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Powered by W3.A while loop statement in Python programming language repeatedly executes a target statement as long as a given condition is true.

Here, statement s may be a single statement or a block of statements. The condition may be any expression, and true is any non-zero value. The loop iterates while the condition is true. When the condition becomes false, program control passes to the line immediately following the loop.

In Python, all the statements indented by the same number of character spaces after a programming construct are considered to be part of a single block of code. Python uses indentation as its method of grouping statements.

how to restart a while loop in python

Here, key point of the while loop is that the loop might not ever run. When the condition is tested and the result is false, the loop body will be skipped and the first statement after the while loop will be executed.

The block here, consisting of the print and increment statements, is executed repeatedly until count is no longer less than 9.

how to restart a while loop in python

With each iteration, the current value of the index count is displayed and then increased by 1. You must use caution when using while loops because of the possibility that this condition never resolves to a FALSE value. This results in a loop that never ends. Such a loop is called an infinite loop. If the else statement is used with a for loop, the else statement is executed when the loop has exhausted iterating the list. If the else statement is used with a while loop, the else statement is executed when the condition becomes false.

The following example illustrates the combination of an else statement with a while statement that prints a number as long as it is less than 5, otherwise else statement gets executed.

Similar to the if statement syntax, if your while clause consists only of a single statement, it may be placed on the same line as the while header. Python while Loop Statements Advertisements.

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You may want to consider using a different type of loop where that logic is applicable, because it is the most obvious answer. Changing the index variable i from within the loop is unlikely to do what you expect. You may need to use a while loop instead, and control the incrementing of the loop variable yourself. Each time around the for loop, i is reassigned with the next value from range.

So something like:. Otherwise, i is incremented as you would expect same as the for loop. Here is an example using a generator's send method :. Just wanted to post an alternative which might be more genearally usable. Most of the existing solutions use a loop index to avoid this.

But you don't have to use an index - the key here is that unlike a for loop, where the loop variable is hidden, the loop variable is exposed. Usuallywhen you think you want to do this, your algorithm is wrong, and you should rewrite it more cleanly. But it is at least possible.

Learn more. Asked 11 years, 2 months ago. Active 4 years, 1 month ago. Viewed 92k times. Is there a way to restart that loop? Greg Hewgill k gold badges silver badges bronze badges.

Active Oldest Votes. Igal Serban 9, 2 2 gold badges 31 31 silver badges 35 35 bronze badges.Sometimes, you may wish to check within a script when a configuration file or the script itself changes, and if so, then automatically restart the script.

In this post, you will see a way of doing this in Python. Consider the following scenario. You have a Python script that runs as a daemon and regularly performs the prescribed tasks. Examples may be a web server, a logging service, and a system monitor. When the script starts, it reads its configuration from a file, and then enters an infinite loop. In this loop, it waits for inputs from the environment and acts upon them.

For example, a web server may react to a request for a page, which results into sending a response to the user. From time to time, it may be necessary to restart the script.

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For example, if you fix a bug in it or change its configuration. One way of doing so is to kill the script and run it again. However, this requires manual intervention, which you may forget to do. When you fix a vulnerability in the script, you want to be sure that you do not forget to restart the script. Otherwise, someone may exploit the vulnerability if you did not restart the script.

It would be nice if there existed a way of restarting the script within itself after it detected that its sources or a configuration file changed. In the rest of this post, we will show such a way. That is, it processes the arguments and loads the configuration from the configuration files. After that, the script waits for inputs and processes them in an infinite loop. When the script starts, we get and store the time of the last modification of these files by using os. If either of the files that we watch has changed, we restart the script.

The restarting is described next. The exact version and arguments depend on how you run the script. For example, on Linux or Mac OS, you can make the file executable by putting the following line to the top of the file.

Either way, do not forget to import the sys module:. To explain, the arguments of os. The os. Instead, it starts executing the current script from its beginning, which is what we want. Therefore, if you have any opened files at the time of restarting the script, you should flush them using f.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Python while Loop Statements

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Is there a command to restart a while loop? I am creating a guessing game but i need to find a way to restart the loop.

Learn more. Asked 7 days ago. Active 7 days ago. Viewed 34 times. James Liew James Liew 19 2 2 bronze badges.

Dhruv jain (djain4)

I would put the "game logic" into a function then put that into a while loop with your question i. And use break to exit external loop - if restart. Active Oldest Votes. The Overflow Blog.

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Write for DigitalOcean You get paid, we donate to tech non-profits. DigitalOcean Meetups Find and meet other developers in your city. Become an author. One way to repeat similar tasks is through using loops.

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A while loop implements the repeated execution of code based on a given Boolean condition. The code that is in a while block will execute as long as the while statement evaluates to True. You can think of the while loop as a repeating conditional statement.

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After an if statement, the program continues to execute code, but in a while loop, the program jumps back to the start of the while statement until the condition is False.

The something that is being done will continue to be executed until the condition that is being assessed is no longer true. While going through this loop, there are two possible outcomes:.

how to restart a while loop in python

Here, the while is followed by the variable password. This means that if the user inputs the string passwordthen the loop will stop and the program will continue to execute any code outside of the loop.

However, if the string that the user inputs is not equal to the string passwordthe loop will continue. Inside of the while loop, the program runs a print statement that prompts for the password. The program will check to see if the variable password is assigned to the string passwordand if it is, the while loop will end.

The last print statement is outside of the while loop, so when the user enters password as the password, they will see the final print statement outside of the loop.

However, if the user never enters the word passwordthey will never get to the last print statement and will be stuck in an infinite loop. An infinite loop occurs when a program keeps executing within one loop, never leaving it. Here is sample output from the program:. Keep in mind that strings are case sensitive unless you also use a string function to convert the string to all lower-case for example before checking.

To best understand how this program works, you should also read about using conditional statements and converting data types. At this point, we can get into our while loop, first initializing a variable and then creating the loop. Within the loop, we added a print statement to prompt the user to enter a number, which we took in with the input function and set to the guess variable. Then, we converted guess from a string to an integer.

Finally, we write a conditional if statement to see if the guess that the user made is equivalent to the number that the computer generated, and if so we use a break statement to come out of the loop. Though it works, right now the user never knows if their guess is correct and they can guess the full 5 times without ever knowing if they got it right.

Sample output of the current program looks like this:. These will go at the end of our current file. At this point, the program will tell the user if they got the number right or wrong, which may not happen until the end of the loop when the user is out of guesses.

These can tell the user whether their number was too low or too high, so that they can be more likely to guess the correct number. When we run the program again with python guess.

So, if the randomly-generated number is 12 and the user guesses 18they will be told that their guess is too high, and they can adjust their next guess accordingly.Loops is where a computer does repetitive tasks. This is where computers become very useful and powerful. Loops have iteration variables that change each time the loop goes through an iteration. Often loops go through a range of numbers. In Python you have the ability to iterate over a list of variables which can be useful in certain operations.

In Python, you get two types of loops namely a while loop and a for a loop. Most prefer to use a for loop when possible as it can be more efficient than the while loop.

The while loop has its use cases. In this tutorial, we will study the while loop and in the next tutorial, we will study the for loop. A while loop in python is a loop that runs while a certain condition is true.

Once the condition changes to false the loop stops. Below is a diagram of a while loop. From top to bottom, the variable t is set to If t is greater than 0 the loop iterates the code in the loop which is printing the value of t to the screen and then decreasing the value of t by 1. Once the code is not indented anymore the while loop code ends. When the diagram is converted to code it looks as follows:. The code in this loop runs 10 times and each time one is subtracted from the variable t.

The while loop runs only when t is greater than 0when t reaches 0 the while loop breaks and the code continues. After the while loop we have the code to print the word Launching.

In the next tutorial we will demonstrate how to use the for loop which is much better suited to an example like this. The conditional statement can be anything that evaluates to True or False. While the conditional statement is true the while loop will iterate. There is a shorter way to increment or decrement an iteration variable:. It is not always necessary to use an iterative variable for the conditional statement in a while loop.

For example, a while loop that runs only while it is raining and as soon as the raining variable is false the while loop stops running. An infinite loop is a loop that does not stop running.


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