range

Properties

>>> dir(range)
['__bool__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'count', 'index', 'start', 'step', 'stop']

Definition

range represents an immutable sequence of evenly spaced integers. It is memory efficient and generates values lazily. Commonly used for loops, indexing, and producing integer sequences without materializing a list.

>>> r = range(2, 10, 2)  # start, stop, step
>>> list(r)
[2, 4, 6, 8]

Using range

Instantiation

>>> range(5)          # 0,1,2,3,4
>>> range(2, 5)       # 2,3,4
>>> range(10, 2, -3)  # 10,7,4

Indexing and slicing

>>> r = range(0, 10, 2)
>>> r[2]
4
>>> r[-1]
8
>>> r[1:3]
range(2, 6, 2)
>>> list(r[1:3])
[2, 4]

Membership

Membership is computed arithmetically, not by iterating.

>>> 6 in range(0, 10, 2)
True
>>> 7 in range(0, 10, 2)
False

Length

>>> len(range(1_000_000_000))
1000000000

Start, stop, step attributes

>>> r = range(3, 9, 2)
>>> r.start, r.stop, r.step
(3, 9, 2)

count and index

>>> r = range(0, 10, 2)
>>> r.count(4)
1
>>> r.count(5)
0
>>> r.index(4)
2

Dunder methods

Dunder Method	Operation	Example (normal syntax)	Example (dunder call)
__len__	Length	len(range(5)) → 5	range(5).__len__()
__getitem__	Index access	range(5)[2] → 2	range(5).__getitem__(2)
__contains__	Membership	3 in range(5) → True	range(5).__contains__(3)
__iter__	Iteration	for n in range(3)	range(3).__iter__()
__eq__	Equality	range(3) == range(0,3)	range(3).__eq__(range(0,3))