Imagine that we have a series of numbers from 0 to 9. We want to add these numbers together. We could do it like this:

sum = 0
i = 0

while i < 10:
    sum += i
    i += 1

print(sum)  # => 45

First, we set the initial sum to 0. Then we run a loop in which the variable i starts taking values starting from 0 and going up to 10. At each step we add the value of i to our sum and increase i by 1. As soon as i becomes equal to 10, the loop ends and the program gives us the sum of all numbers from 0 to 9 equal to 45.

We can rewrite this code into a for loop

sum = 0

for i in range(10):
    sum += i

print(sum)  # => 45

The first example uses while, which keeps running until i < 10. The second uses for and iterates from 0 to 9 using range(). Both do the same thing: add the numbers from 0 to 9 to the sum variable, but they use different ways to iterate.

The range() function

The range function in Python is a built-in function that creates a sequence of numbers within a specific range. It can be used in a for loop to control the number of iterations.

range() has several uses:

• range(stop) creates a sequence from 0 to stop - 1.
• range(start, stop) creates a sequence from start to stop - 1.
• range(start, stop, step) creates a sequence of numbers from start to stop - 1, with step step.

We saw the example with one final value above. Let's consider another one - print the numbers from 1 to 3 to the screen:

for i in range(1, 4):
    print(i)

# => 1
# => 2
# => 3

Now let's try to output the numbers in reverse order

for i in range(3, 0, -1):
    print(i)

# => 3
# => 2
# => 1

In the examples above, we can see that the iteration completes to a final value

Implement the print_table_of_squares(from, to) function that prints squares of numbers to the screen. It first from and last to a number prints the string square of <number> is <result>

Call examples:

print_table_of_squares(1, 3)
# => square of 1 is 1
# => square of 2 is 4
# => square of 3 is 9