# Python for loop decrementing index

In this tutorial, let’s look at for loop of decrementing index in Python.
A for loop in python is used to iterate over elements of a sequence. It is mostly used when a code has to be repeated ‘n’ number of times. In general, for loop in python is auto-incremented by 1. What if you want to decrement the index. This can be done by using “range” function. Let’s look at it in detail.

## Range Function in Python

Range function returns a new list of numbers within the specified range. Note that Range() function can be used for only for integers.
Example of simple range function:

```for x in range(3):
print(x)```

Output:

```0
1
2```

Here, all the numbers from 0(zero) till the specified range(i.e. 3 here) are printed.

What if we want to start the loop from some other number rather than zero, then we can use the range function as shown below.
Syntax for range:

`range(start index, stop index, step)`

Here, start and step are optional arguments. As seen in previous example only stop value is given and it starts from 0(by default) also its step is 1(by default)

## Decrementing the index value in Python

If the user wants to decrement the index value inside for loop then he/she should make the step value negative. By making the step value negative it is possible to decrement the loop counter.

Example:

```for x in range(10,0,-2):
print(x)```

Output:

```10
8
6
4
2```

As it is observed, initial value of x is 10 and it goes on decrementing till 0 with the step value -2.

#### Conclusion

• InĀ for loop, index is by default incremented by 1.
• To decrement the index in for loop, make the step value negative.

Hope you got an idea on the topic “Decrementing index in for loop in Python”

### One response to “Python for loop decrementing index”

1. Rajesh says:

Can you explain below?

a=[1,2,3,4,5]
for a[-1] in a:
print(a[-1])
Output:
1
2
3
4
4

print(a)
[1, 2, 3, 4, 4]