python内置函数之slice案例详解_Python

英文文档：

class slice(stop) class slice(start, stop[, step]) Return a slice object representing the set of indices specified by range(start, stop, step). The start and step arguments default to None. Slice objects have read-only data attributes start, stop and step which merely return the argument values (or their default). They have no other explicit functionality; however they are used by Numerical Python and other third party extensions. Slice objects are also generated when extended indexing syntax is used. For example: a[start:stop:step] or a[start:stop, i]. See itertools.islice() for an alternate version that returns an iterator.

说明：

　　1. 函数实际上是一个切片类的构造函数，返回一个切片对象。

　　2. 切片对象由3个属性start、stop、step组成，start和step默认值为None。切片对象主要用于对序列对象进行切片取对应元素。

				?

									>>> help(slice)

									class slice(object)

									 |  slice(stop)

									 |  slice(start, stop[, step])

									 |  

									 |  Create a slice object.  This is used for extended slicing (e.g. a[0:10:2]).

									 |  

									 |  Methods defined here:

									 |  

									 |  ...#省略#

									 |  ----------------------------------------------------------------------

									 |  Data descriptors defined here:

									 |  

									 |  start

									 |  

									 |  step

									 |  

									 |  stop

									 |  

									 |  ----------------------------------------------------------------------

									 |  Data and other attributes defined here:

									 |  

									 |  __hash__ = None

				?

									>>> a = list(range(10))

									>>> a

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

									>>> a[None:5:None] # start step显式为None

									[0, 1, 2, 3, 4]

									>>> a[:5:] # start step默认为None

									[0, 1, 2, 3, 4]

									>>> a[2:5:None] # step显式为None

									[2, 3, 4]

									>>> a[2:5:] # step默认为None

									[2, 3, 4]

									>>> a[1:10:3]

									[1, 4, 7]

　　3. 对应切片对象的3个属性start、stop、step，slice函数也有3个对应的参数start、stop、step，其值分别会付给切片对象的start、stop、step。

				?

									>>> c1 = slice(5) # 定义c1

									>>> c1

									slice(None, 5, None)

									>>> c2 = slice(2,5) # 定义c2

									>>> c2

									slice(2, 5, None)

									>>> c3 = slice(1,10,3) # 定义c3

									>>> c3

									slice(1, 10, 3)

									>>> a[c1] # 和a[:5:]结果相同

									[0, 1, 2, 3, 4]

									>>> a[c2] # 和a[2:5:]结果相同

									[2, 3, 4]

									>>> a[c3] # 和a[1:10:3]结果相同

									[1, 4, 7]

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原文链接：https://www.cnblogs.com/sesshoumaru/p/6063975.html

python内置函数之slice案例详解

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