range用法
range用法
class range(stop) # start 默认为0, step默认为1
class range(start, stop [, step] )
2
1
class range(stop) # start 默认为0, step默认为1
2
class range(start, stop [, step] )
step > 0时,一个 range 的元素值为 r[i] = start + i * step , r[i] < stop;
step < 0时,r[i] > stop。
>>>range(6)
[0, 1, 2, 3, 4, 5]
>>>range(0,-10,-2)
[0, -2, -4, -6, -8]
4
1
>>>range(6)
2
[0, 1, 2, 3, 4, 5]
3
>>>range(0,-10,-2)
4
[0, -2, -4, -6, -8]
用法1: arrary[x : -y : s]
list中从第x到第倒数y个数,间隔s。 x,y默认0, s默认1
当S < 0 时,为从后向前,此时x需要在y之后
>>> array = [0,1,2,3,4,5,6]
>>> array[0:]
[0, 1, 2, 3, 4, 5, 6]
>>> array[1:]
[1, 2, 3, 4, 5, 6]
>>> array[2:]
[2, 3, 4, 5, 6]
>>> array[:-1]
[0, 1, 2, 3, 4, 5]
>>> array[:-3]
[0, 1, 2, 3]
>>> array[3:-3]
[3]
>>> array[::-1]
[6, 5, 4, 3, 2, 1, 0]
>>> array[1::-1]
[1, 0]
>>> array[-1:4:-1]
[6, 5]
19
1
>>> array = [0,1,2,3,4,5,6]
2
>>> array[0:]
3
[0, 1, 2, 3, 4, 5, 6]
4
>>> array[1:]
5
[1, 2, 3, 4, 5, 6]
6
>>> array[2:]
7
[2, 3, 4, 5, 6]
8
>>> array[:-1]
9
[0, 1, 2, 3, 4, 5]
10
>>> array[:-3]
11
[0, 1, 2, 3]
12
>>> array[3:-3]
13
[3]
14
>>> array[::-1]
15
[6, 5, 4, 3, 2, 1, 0]
16
>>> array[1::-1]
17
[1, 0]
18
>>> array[-1:4:-1]
19
[6, 5]
xrange
在Python 3中,range()与xrange()合并为range( )。