Python range and arguments (start, stop, and step)

You can get consecutive integers by the range(), a Python built-in function.

r = range(4)

for n in r:
    print(n)

# 0
# 1
# 2
# 3

It returns the range object similar to list.

r = range(4)

print(r)  # range(0, 4)
print(type(r))  # <class 'range'>

range()

The range() can take arguments in two patterns.

  • stop
  • start, stop, (step)

The first pattern has only the stop argument. The second pattern has the start, stop, and step arguments and the step is optional.

a = range(4)
b = range(3, 10)
c = range(3, 10, 2)

a2 = list(a)
b2 = list(b)
c2 = list(c)

print(a2)  # [0, 1, 2, 3]
print(b2)  # [3, 4, 5, 6, 7, 8, 9]
print(c2)  # [3, 5, 7, 9]

Negative step

a = range(0, -4, -1)
b = range(3, -10, -1)
c = range(3, -10, -2)

a2 = list(a)
b2 = list(b)
c2 = list(c)

print(a2)  # [0, -1, -2, -3]
print(b2)  # [3, 2, 1, 0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
print(c2)  # [3, 1, -1, -3, -5, -7, -9]

Negative step means the negative direction.

Reverse the range

a = range(5)[::-1]
b = range(7, 10)[::-1]
c = range(7, 25, 4)[::-1]

a2 = list(a)
b2 = list(b)
c2 = list(c)

print(a2)  # [4, 3, 2, 1, 0]
print(b2)  # [9, 8, 7]
print(c2)  # [23, 19, 15, 11, 7]

You can reverse the range using Python slicing [::-1]. This syntax is used to reverse a list, tuple, string, etc.

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