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Python range()

The built-in function range() is used to return a sequence of integer numbers by specifying starting and ending points in the sequence. This resultant sequence is immutable means values cannot be changed. For repeating a  task a specific number of times we can use this range() method with loops.

range(start, stop[, step]) #where stop is an integer indicates stop position.

range() Parameters:

Takes three parameters. If the start index is not given it starts from 0, and it will increment the value by 1 continue until the stop index.

Parameter Description Required / Optional
start  An integer number specifying at which position to start. Default is 0 optional
stop  An integer number specifying at which position to stop Required
step  An integer determines the increment between each integer in the sequence optional

range() Return Value

The result sequence is starting from 0 to stop - 1.if the stop is negative or 0 it returns an empty sequence.

r[n] = start + step*n (for both positive and negative step)
where, n >=0 and r[n] < stop (positive step)
where, n >= 0 and r[n] > stop (negative step)

If the step is zero it raises a ValueError exception. If non zero it returns a sequence according to the formula. If it doesn't meet the value constraint, an empty sequence is returned.

Input Return Value
 integer  integer sequence

Examples of range() method in Python

Example 1: How range works in Python?

# empty range

# using range(stop)

# using range(start, stop)
print(list(range(1, 10)))


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

Example 2: Create a list of even number between the given numbers using range()

start = 2
stop = 14
step = 2

print(list(range(start, stop, step)))


[2, 4, 6, 8, 10, 12]

Example 3: How range() works with negative step?

start = 2
stop = -14
step = -2

print(list(range(start, stop, step)))

# value constraint not met
print(list(range(start, 14, step)))


[2, 0, -2, -4, -6, -8, -10, -12]