What is an infinite loop in python

What is Infinite Loop in Python?

Before learning about the infinite loop in Python, let us first understand the term loop in Python.

A loop is a sequence of iterative statements or instructions that are continuously repeated until a certain condition meets. Loops are used in scenarios where we want to do certain work numerous times. So instead of writing the same code multiple times, we use a loop.

There are mainly two kinds of loops in Python namely the for loop and the while loop.

Refer to the image below to understand the working of the loop using a flow chart.

Now, coming back to the topic, an infinite loop in Python is a continuous repetition of the conditional loop until some external factors like insufficient CPU memory, error in the code, etc. occur.

There are various types of infinite loops in Python such as:

An infinite loop does not have an explicit end (no loop termination condition is specified by the programmer).

In the above code, the Scaler Topics is printed an infinite number of times. Now, we can terminate the execution using CTRL + C so that the memory of the CPU does not get exhausted.

The output that will be shown when we terminate the execution is:

When are Infinite Loops Necessary?

In Python, an infinite loop can be useful in various scenarios. One of the prime use of an infinite loop can be seen in a client-server architecture model in networking.

As we know a server is central storage that is always awake and ready to handle client requests. So, a server runs in an infinite loop which makes it always awake and ready to handle various situations like new requests from the client, new connections from the client, etc.

Another example of an infinite loop in Python can be visualized in game development. For example, an infinite while loop is used for the main game frame which continues to get executed until the user or the game selects some other event. Since the game developer does not know the exact iterations or the time at which the user will do something, the game developer uses the infinite loop in Python.

There are several other scenarios in which we explicitly use the infinite loop in Python, refer to the following sections for examples and code implementation.

How Would an Infinite Loop be Run by Mistake?

Suppose we are given a program to print a certain thing 10 times. We can use a while loop to print the output.

The idea of the program is very simple, we will use a counter (initialized with 0) that will increment in each iteration and print the result. We can insert a termination condition that will terminate the loop once the counter reaches 10.

Suppose we have written the code correctly but missed out on the increment statement. So, the code results in an infinite loop as the counter break condition will never reach.

Let us see the implementation.

To avoid this issue, we need to increment the counter so that the loop will get terminated at a certain specified condition.

Kinds of Infinite Loop in Python

We have mainly three types of infinite loops in Python. They are:

• The fake infinite loops
• The intended infinite loops
• The unintended infinite loops

Let us discuss them one by one briefly.

1. The Fake Infinite Loops

A fake infinite loop is a kind of loop that looks like an infinite loop (like while True: or while 1: ) but has some certain condition that will terminate the loop.

For example, we are given a program in which we need to print all the even multiples of 3 that is less than and equal to a given number n . Now, at the very start of the code, we cannot know the number of times we need to execute the loop.

So, we will make it an infinite loop but inside the loop, we will insert a condition that will terminate the loop when the number n is encountered.

Let us code the program for better understanding.

As we can see in the code above, we have run an infinite loop and inside the infinite loop, we have used an if statement that will work as the terminating condition of the loop.

2. The Intended Infinite Loops

In some scenarios, we need to use an infinite loop to correctly execute the program. Suppose, we need to make a counter then we must use an intended infinite loop in Python.

Let us implement the above program for better understanding.

In the above program, we ran an infinite loop and in each iteration, the timer will keep on increasing.

3. The Unintended Infinite Loops

Another variant of the infinite loop in Python can be the unintended infinite loop. As the name suggests, if we have made a silly mistake and have not added any loop terminating condition then the loop becomes an unintended infinite loop in Python.

Let us take an example program to understand the content better.

In the above program, we made a mistake by not adding any termination condition as well as we have not incremented the counter than can break the loop. So, it resulted in an unintended infinite loop.

Types of Statements in Python Infinite Loop

A statement in Python is used for creating variables or for displaying values. A statement is not evaluated for some results. Example: x = 3 .

We can use the various states with an infinite loop in Python. Let us understand the various statement used with the infinite loops in Python with example(s).

1. While Statement in Python Infinite Loop

We can use the while loop in Python to create an infinite loop in Python as we have seen in the above examples. Now, we generally use two types of statements to create an infinite loop in Python. Let us see both of these statements using code examples:

a. Using while 1:

b. Using while True:

2. Using IF Statement with While Loop

Now, as we have seen above, we used the while loop to run an infinite loop in Python. Now to terminate the infinite loop, we can use an if statement that will check some conditions. Now, if the condition is satisfied, then we can perform something like terminating the loop.

Let us code an example for better understanding.

3. Using Break Statement

As the name suggests, the break statement is used to break or terminate the currently executing loop.

Let us take an example to understand the working of the break statement better.

4. Using Continue Statement

The continue statement is used to shift to the next iteration of the loop. So, whenever we want to skip a certain condition and we want to execute the rest of the execution, we can use a continue statement.

Let us take an example to understand the working of the continue statement better.

How to Create an Infinite Loop in Python?

We can create an infinite loop in Python (or other programming languages) using the while loop. In general, the for loop is not used for creating infinite loops as the for loop statement contains the termination condition.

Suppose we are given a program to print the square of a number provided by the user. Now, we can write a program something like this:

Now, the above code is completely correct but we need to run the code every time a new input has to be provided. So, to avoid such a problem, we can write an infinite loop that will print the square of a number every time the user inputs a new number.

Let us see how we can convert the above code into an infinite loop using the while loop.

Heads or Tails Game

A real-life use case of the infinite loop can be the head and tails game. Various games need a toss (random selection of head or tail) that decides which team will start the game first (for example in a cricket game, the toss decides which team will be allowed to select the batting or bowling).

So, to make a head and tail game, we can use an infinite loop that will randomly choose between head or tail every time user demands a selection.

We can use the Python random module for the same. Let us see the implementation for a better understanding.

In the above code, we are using the random module’s choice() function that will randomly select among the list of choices. Now, if the user enters N or n then the if condition is satisfied and the loop is terminated.

To learn more about the random module and other modules in Python, refer to here.

Finite vs. Infinite Loop in Python

Let us now discuss the basic differences between the finite loop and infinite loop in Python.

Infinite Loop	Finite Loop
An infinite loop in Python iterates an infinite number of times.	The finite loop in Python iterates a finite number of times.
Some external factors like insufficient CPU memory, error in the code, etc. can terminate the infinite loop in Python.	Finite loop in Python has the predefined terminating condition.
An infinite loop in Python is used to run a certain program or block of code an unspecified number of times.	A finite loop in Python is used to run a certain program or block of code a certain number of times.
Example: while True:	Example: for i in range(5):

Learn more

To learn more about the Python programming language and other Python-related topics, please refer to the links specified below:

Conclusion

• A loop is a sequence of continuously repeated instructions until a certain condition meets. Loops are used in scenarios where we want to do a certain work numerous time
• There are mainly two kinds of loops in Python namely the for loop and the while loop.
• An infinite loop in Python is a continuous repetition of the conditional loop until some external factors like insufficient CPU memory, error in the code, etc. occur.
• An infinite loop does not have an explicit end (no loop termination condition is specified by the programmer).
• An infinite loop in Python can be useful in various scenarios. One of the prime use of an infinite loop can be seen in a client-server architecture model in networking.
• We have mainly three types of infinite loops in Python:
  • The fake infinite loops
  • The intended infinite loops
  • The unintended infinite loops

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  Python Infinite Loop

  

  Infinite Loop is a loop that does not end. Infinite loops consist of repetitive steps which condition require repeating always. Python provides different ways for infinite loops. The while statement can be used for the infinite loop in Python. But before using Python infinite loops keep in mind that the infinite loops use a lot of system resources like CPU, Memory which may cause system crashes or performance problems.

  Infinite Loop with while

  One of the most popular and easy way to implement infinite loop in Python is using the while statement. The while statement has the following syntax where the condition is used to control steps and iterations. By providing allways true condition to the while loop this will be an infinite loop.

  • CONDITON is used to control while loop. We will set the CONDITION true for allways in order to create infinite loop with while.
  • BLOCK is the body of the while infinite loop which will be executed in every step or iteration.

  The most easy way is setting the condition as True for the while loop.

  while True: print("This is infinite loop")

  We can see the following output that the same output printed again and again.

  

  Stop Infinite Loop

  The infinite loop continues unless it is killed, stopped. There are different ways to stop the infinite loop. The CTRL+C key shortcut can be used to kill the infinite loop. While the infinite loop is executing press CTRL+C at the same time. We can see that the KeyboardInterrupt is printed as the infinite loop is interrupted.

  This is infinite loop This is infinite loop This is infinite loop This is infinite loop This is infinite loop This is infinite loop This is infinite loop This is infinite loop ^CTraceback (most recent call last): File "", line 2, in KeyboardInterrupt This is infinite loop

  Infinite Loop with if

  Infinite loop is created to iterate to infinite but in some cases, we may want to check some conditions in every iteration. The if statement or conditional can be used to check every step of the infinite loop. In the following example, we check if the current number is odd or not by using the if statement.

  number=0 while True: if (number%2) == 1: print(number "is odd")

  Break Infinite Loop

  In some cases, we may need to break the infinite loop. Even it may seem that this is not an infinite loop the breaking infinite loop is an exceptional case. The break statement can be used to break the infinite loop. The break statement also used with the if statement in order to break the infinite loop for specific cases. In the following example if the square of the number is greater than 10000 the infinite loop ended.

  number=0 while True: if (number*number) > 10000: break

  Skip Steps In Infnite Loop

  Another useful case for the infinite loop is skipping some steps. The continue statement can be used to skip some steps with the if statement. In the following example we will skip odd numbers by using continue in the infinite loop.

  number=0 while True: if (number%2) == 1: continue print(number "is even")

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