What does range mean in python?

In python, range means "range" and "series". It is a built-in function used to generate a series of consecutive integers and create a list of integers. The syntax is "range(start,stop [,step])"; its integer list ranges from the start value to the stop value, but does not include stop.

#The operating environment of this tutorial: Windows 7 system, Python 3 version, Dell G3 computer.

Range means "range" or "a series".

python range()

range is a built-in function in python that is used to generate a series of consecutive integers and create a list of integers , generally used in for loops.

range() function syntax

range(start, stop[, step])

Parameter description:

start: Counting starts from start. The default is to start from 0. For example, range(5) is equivalent to range(0, 5);

stop: counts to the end of stop, but does not include stop. For example: range (0, 5) is [0, 1, 2, 3, 4] without 5

step: step size, default is 1. For example: range(0, 5) is equivalent to range(0, 5, 1)

Example

>>>range(10)        # 从 0 开始到 10
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> range(1, 11)     # 从 1 开始到 11
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> range(0, 30, 5)  # 步长为 5
[0, 5, 10, 15, 20, 25]
>>> range(0, 10, 3)  # 步长为 3
[0, 3, 6, 9]
>>> range(0, -10, -1) # 负数
[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
>>> range(0)
[]
>>> range(1, 0)
[]

The following is the use of range in for, looping out each letter of runoob:

>>>x = 'runoob'
>>> for i in range(len(x)) :
...     print(x[i])
... 
r
u
n
o
o
b
>>>

Analysis

(1)range() is an iterable object, but not an iterator.

As shown below:

Supplement:

Iterable object (Iterable):

All objects that can be used in for loops are iterable objects, which can be judged by Iterable in the collections module.

Iterator (Iterator):

can not only be used on for loops, but also can be used on the next() function. The object is an iterator, which represents a sequence of lazy calculations and can be used in the collections module. Iterator to judge.

If the iterable object wants to become an iterator, you can use the iter() function:

iter(range(3))

When the for loop traverses, the iterable object and the iterator The performance of the processors is the same, that is, they are all evaluated lazily, and there is no difference in space complexity and time complexity. The difference between iterable objects and iterators is "the same thing but two different things": the same thing is that both can be lazily iterated (__Iter__ method), the difference is that iterable objects do not support self-traversal (that is, __next__ method), and the iterative The processor itself does not support slicing (i.e. __getitem__ method).

(2)range() is an immutable sequence type. It can perform operations such as judging elements, finding elements, slicing, etc., but it cannot modify elements.

In short: range() is an iterable object rather than an iterator, and the range object is an immutable arithmetic sequence.

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