The range Function in Python: Description and Examples

The range function returns a sequence of numbers within a specified range with a defined step. These sequences are typically used in for loops to iterate over numbers.

Syntax and Parameters¶

range(stop)¶

range(start, stop, step=1)¶

• start — starting value of the sequence (default is 0).
• stop — end value of the sequence (not included).
• step — step of the sequence (default is 1).

Passing a single argument means you’re providing the stop value, not the start.

Usage Examples¶

In the example below, a sequence of numbers from 0 to 5 (excluding 5) is created. The for loop iterates over this sequence:

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

0
1
2
3
4

To set the starting value, use two arguments:

for i in range(2, 5):
    print(i)

2
3
4

Pass a third argument to specify the step:

for i in range(0, 10, 2):
    print(i)

0
2
4
6
8

To create a sequence in reverse order, use a negative step. For example, a sequence from 5 to 1 can be created as follows:

for i in range(5, 0, -1):
    print(i)

5
4
3
2
1

Indexing, Slices, and Conversion to a List¶

The range() function returns an iterable object that supports indexing and slicing:

numbers = range(10)
print(numbers)          # range(0, 10)
print(numbers[2])       # 2
print(numbers[2:5])     # range(2, 5)

To get an actual list of numbers, use the list() function to convert the range object:

numbers = list(range(5))
print(numbers)          # [0, 1, 2, 3, 4]

while and a Counter Variable or for and range?¶

To iterate over a sequence of numbers, use either a while loop with a counter variable or a for loop with range(). Using a for loop with range() is generally preferable as it makes the code more readable. Compare the example using a while loop and a counter variable with the example using a for loop and range():

# Using a while loop and a counter variable
i = 0
while i < 5:
    print(i)
    i += 1

# Using a for loop and range
for i in range(5):
    print(i)