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Python range() Function

Video link: https://youtu.be/muKeRgZ9LnU

In this video, we learned about the Python range() function that returns a sequence.

Programs in the Video

Using range()

Suppose, we want a sequence of numbers from 1 and 10. To get this sequence, we can use the range() function like:

result = range(1, 11)
print(result)

Output

range(1, 11)

The range() function returns a range object which is a sequence of numbers. We can see what is inside this object by converting it to other types like list.

result = range(1, 11)

# converting to list
result = list(result)

print(result)

Output

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Notes:

  • Here, the start of the sequence 1 is inclusive, but the end 11 is exclusive. That's why it gives us a sequence from 1 up to 10, and not 1 up to 11.
  • By default, the step between the numbers (difference between two consecutive elements) is 1.

range() in for Loop

Since range() generates a sequence of numbers, it is commonly used with for loops to iterate over the loop a certain number of times.

For example,

for value in range(1, 6):
    print(value, "iteration")

Output

1 iteration
2 iteration
3 iteration
4 iteration
5 iteration

range() with only stop Parameter

In our examples up to now, we have passed two parameters to the range() function:

  • start - start of the sequence
  • stop - end of the sequence (exclusive)

It is also possible to use range() without passing the start parameter. If the start parameter is not passed, 0 is used as its default value.

result = range(11)

result = list(result)
print(result)

Output

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

To iterate a loop 5 times we can now simply use:

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

Output

0
1
2
3
4

range() with step Parameter

By default, the difference between two consecutive numbers in the sequence is 1.

For example,

result = list(range(1, 11))
print(result)

Output

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

It is because the default value of the step parameter of the range() function is 1. The above code is equivalent to:

result = list(range(1, 11, 1))
print(result)

If we change the step argument to 3:

result = list(range(1, 11, 3))
print(result)

Output

[1, 4, 7, 10]

We can also use negative numbers in the range function:

result = list(range(5, -6, -1))
print(result)

Output

[5, 4, 3, 2, 1, 0, -1, -2, -3, -4, -5]

Note: range() only works for integers. We cannot use floating-point numbers inside the range() function.

Programming Task

Can you create the following list using the range function?

[3, 6, 9, 12, 15, 18, 21, 24, 27, 30]

sequence = range(3, 31, 3)

print(list(sequence))

Output

[3, 6, 9, 12, 15, 18, 21, 24, 27, 30]