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This article deals with one of the most widely used built-in function of Python,
that is **range()** function. You'll learn all about **range()** function, step by
step in this tutorial. This tutorial deals with:

- What is range() Function
- Syntax of range() Function
- Example Programs of range() Function
- range() Function with Two Arguments
- range() Function with Three Arguments
- range() Function to generate sequence in Reverse
- Generate sequence using range() based on user's requirement

Don't skip this tutorial, until getting complete understanding on **range()**, as it plays like a trump card in most of the
program created using **loops**

As name suggests, **range()** creates/generates a sequence of numbers. That is, using **range()**, we can generate some set
of numbers. The order of sequence is defined through its argument(s) passed.

Most of the time, **range()** used in **for** loop. Since **for** loop is used to execute some set of statements,
some required number of times. And **range()** helps to do that type of task.

The syntax of using **range()** function is:

`range(start, stop, increment_by)`

The first (**start**) and third (**increment_by**) arguments are optional. Let's understand about all the three arguments
in detail.

Here **start** indicates the number/value from where the generation of sequence of numbers gets started. And **stop** is
the number/value that indicates the stoppage of generation of sequence of number. Finally, the third argument, that is **increment_by**
is the value that is used to increment the sequence of numbers by this value.

**Keep in Mind** - **start** is included, whereas **stop** is excluded. For example, **range(10, 15)** gives
10, 12, 13, 14. Don't worry, you'll get to know about its working later on, in this tutorial.

In all the three arguments, the second one, that is **stop** is necessary. That is:

- If there is only one argument passed to
**range()**, then it gets treated as**stop** - If there are two arguments passed to
**range()**, then the first argument gets treated as**start**, whereas the second argument indicates to**stop** - And if there are three arguments passed to
**range()**, then first is for**start**, second is for**stop**, and third argument is the value that is used to increment the sequence by its value, every time

If you're not getting an idea, on what I'm trying to say, then just read it and continue. Because after looking at some of the examples given below, I'm sure, you'll get to know everything about the topic.

**Important** - The default value of **start** is 0, whereas **increment_by** is 1. That is, if you do not provide these
two arguments to **range()**. Or if you provide only one argument to it, then that one argument is for **stop**. But **start**
automatically gets initialized with 0, where as **increment_by** automatically gets initialized with 1.

**Note - **All of the three arguments must be an integer. That is, don't pass any argument as real numbers like 1.4, 5.2 etc.

Since programming is the thing, that can not be learn by theory only, as it must requires practical implementation of the code given
in theory part. Therefore, I've provided almost all the programs that uses total variety of **range()** function. Let's start with
very basic one:

nums = range(10) for n in nums: print(n)

The output produced by above program is:

In above program, the statement:

nums = range(10)

generates a sequence of numbers, that are from 0 to 10, where 0 is included but 10 is not. Since I've not provided rest of the two
arguments. Therefore, the **start** gets automatically initialized with 0, whereas **increment_by** initialized with 1. That is,
the generation of sequence of numbers, gets started with 0, and increment by 1 each time. This process continues until 1 less than the
number (**stop**'s value).

Now let's change the above program with the program given below:

nums = range(10) print(nums)

With this program, you'll get following output:

That shows, if you iterate **nums**, then you will get a sequence of numbers starting with 0, and ends with 9 (included), like
shown in the previous program's sample output. You can also directly use **range()** function (in **for** loop) like shown in the
program given below:

for n in range(10): print(n)

You'll get the same output, that is, a sequence of numbers from **0** to **9**. You can also create **list** using
**range()** function, like shown in the program given below:

nums = list(range(10)) print(nums)

Now the output produced by above program is:

The same program can also be replaced with:

nums = range(10) nums = list(nums) print(nums)

The output will be same as of previous program.

Since all the above example programs of **range()** function is based on only argument. Therefore let's start with providing more
than one arguments like shown in the very basic example given below:

for n in range(1, 10): print(n)

Because I've provided two arguments to **range()**. Then first argument automatically gets treated as **start**'s value, whereas
the second argument automatically gets treated as **stop**'s value. Therefore the above program produces the output like shown in the
snapshot given below:

As you can see from above sample output, the program produces a sequence of number, that is from **1** to **10**, not **0**
to **9**. Because I've provided **1** as the number to start the sequence with.

Now let's use all the three arguments:

for n in range(0, 50, 5): print(n)

The above program produces the following output:

As you can see, the third argument is **5**, therefore each time the sequence gets incremented by 5.

The **range()** function can also be used to generate/create sequence of numbers in reverse. To do this task, these are the two basic
things, that must be followed while doing this task:

- The first argument must be greater than second
- The third argument must be with minus (-) sign

Let's take a very basic example, that generates sequence of numbers using **range()** in reverse, of course:

nums = range(10, 0, -1) print(list(nums))

The **range(10, 0, -1)** indicates that the sequence gets started with **10**, decremented by **1** (because I've used -1),
and continues generating the sequence of numbers before 0. Here is the output produced by above program:

Here is another program:

nums = range(100, 0, -10) print(list(nums))

This will generate/prints **[100, 90, 80, 70, 60, 50, 40, 30, 20, 10]**.

**Note - **Always use **minus (-)** for the third argument. That is **increment_by** must gets replaced with a value along
with **minus (-)**.

This is the master program for you, that helps you to understand about **range()** function completely. Let's have a look at the
example program and its sample run given below:

print("Enter the value to start with: ") start_value = int(input()) print("Enter the value to end before: ") stop_value = int(input()) print("Enter the value to increment by, each time: ") increment_by_value = int(input()) print("\nGenerating sequence of numbers, based on your requirement:") for n in range(start_value, stop_value, increment_by_value): print(n)

Here is its sample run with user inputs **24** (as value to start with), **37** (as value to end before), and
**3** (as value to increment by):

Here is another sample run with user inputs, **37**, **24**, and **-3**:

Now I think, you've got the complete understanding about **range()** function in Python. That is very good, as it is going to
use a lot of times while you program in Python.

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