for Loop with Range in Python

This article will teach you how to use the Python for loop to execute a code block a set number of times.

In programming, it’s common to wish to run a block of code several times. A for loop is used to accomplish this.

The syntax of a for loop is illustrated below:

for index in range(n):
    statement

The index is referred to as a loop counter in this form. And n is the number of times the statement will be executed by the loop.

You don’t have to call the loop counter index; you can call it whatever you want.

Python has a built-in function called range(). It’s similar to the print() method in that it’s always present in the programme.

range(n) returns a list of n numbers beginning at zero. It gradually increases the value until it reaches n.

As a result, range(n) generates the following numbers: 0,1, 2,…n-1. It’s worth noting that it’s always less than the total (n).

The following example explains how to display 5 integers from 0 to 4 on the screen using the for loop and the range() function:

for index in range(5):
    print(index)

Output

0 1 2 3 4

The print(index) statement is executed five times in this example by the for loop.

You can perform something like this to display 5 numbers from 1 to 5 on the screen:

for index in range(5):
    print(index + 1)

Output

1 2 3 4 5

In this example, we publish the index after increasing it by one in each iteration. There is, however, a better method to go about it.

Specifying the sequence’s initial value in Python

The range() function starts the sequence with a value of zero by default.

You can also use the range() method to specify a starting number, such as this:

range(start, stop)

The range() function increases the start value by one until it reaches the stop value in this syntax.

The following example utilises a for loop to display five integers on the screen, ranging from 1 to 5.

for index in range(1, 6):
    print(index)

Output

1 2 3 4 5

Specifying the sequence’s increment in Python

In each loop iteration, the range(start, stop) increments the start value by one by default.

To change the start value by a different number, use the range() method in the following format:

range(start, stop, step)

You can give the value that the range() function should increase in this fashion.

The sample below shows all of the odd numbers from 0 to 10:

for index in range(0, 11, 2):
    print(index)

Output

0 2 4 6 8 10

How to Calculate sum of Sequence in Python?

The for loop statement is used in the following example to calculate the sum of values from 1 to 100:

sum = 0
for num in range(101):
    sum += num

print(sum)

Output

5050

How does it work?

The sum is first set to zero.
Second, in each repetition, the sum is multiplied by an integer between 1 and 100.
Finally, project the total onto the screen.
If you’re a mathematician, you can use the following formula:

n = 100
sum = n * (n+1)/2
print(sum)