切片魔术方法

最新推荐文章于 2025-06-11 09:29:40 发布

原创最新推荐文章于 2025-06-11 09:29:40 发布 · 307 阅读

0 ·

CC 4.0 BY-SA版权

Linux 同时被 2 个专栏收录

89 篇文章

订阅专栏

python

29 篇文章

订阅专栏

本文详细介绍了Python中自定义类实现切片操作的方法，包括获取切片__getslice__、设置切片__setslice__及删除切片__delslice__的具体应用。通过实例展示了如何在自定义类中运用这些特殊方法来实现对内部数据的有效管理和操作。

getslice(self,i,j)参数为切片索引，步长可有可无

class Student(object):
    def __init__(self,name):
        self.name=name
        self.score=[10,11,12,13,14,15]

    def __getslice__(self,i,j):
        return self.score[i,j]

s=Student('老李')
print s.score[:3]
print s.score[::-1]
---->>>结果
[10, 11, 12]
[15, 14, 13, 12, 11, 10]

当然也可以加入切片的步长

class Student(object):
    def __init__(self,name):
        self.name=name
        self.score=[10,11,12,13,14,15]

    def __getslice__(self,i,j,step):
        return self.score[i,j,step]

s=Student('老李')
print s.score[:5:2]
--->>结果
[10, 12, 14]

将以上切片出来的成绩保存到/tmp/file中

class Student(object):
    def __init__(self,name):
        self.name=name
        self.score=[10,11,12,13,14,15]

    def __getslice__(self,i,j,step):
        new_score= self.score[i,j,step]

s=Student('老李')
f=open('/tmp/file','w')
li=[]
li.append(s.score[:5:2])
f.write(str(li))
f.close()

设定切片值setslice(self,i,j,item)

这样直接修改会报错

class Student(object):
    def __init__(self,name):
        self.name=name
        self.score=[10,11,12,13,14,15]

    def __getslice__(self,i,j,step):
        return self.score[i,j,step]

s=Student('老李')
print s.score[:5:2]
s[0:2]=[100,111]
print s.score
---->>
[10, 12, 14]
Traceback (most recent call last):
  File "/Python/root/day08.py", line 125, in <module>
    s[0]=100
TypeError: 'Student' object does not support item assignment

使用魔函数setslice(self,i,j,item)

class Student(object):
    def __init__(self,name):
        self.name=name
        self.score=[10,11,12,13,14,15]

    def __getslice__(self,i,j,step):
        return self.score[i,j,step]

    def __setslice__(self, i, j, sequence):
        self.score[i:j]=sequence
s=Student('老李')
print s.score[:5:2]
s[0:2]=[100,111]
print s.score
---->>结果
[10, 12, 14]
[100, 111, 12, 13, 14, 15]

只修改第一个元素s[0]=[100]会报错，需要写成s[:0]=[100]定义setslice函数时参数是i和j

class Student(object):
    def __init__(self,name):
        self.name=name
        self.score=[10,11,12,13,14,15]

    def __getslice__(self,i,j,step):
        return self.score[i,j,step]

    def __setslice__(self, i, j, sequence):
        self.score[i:j]=sequence
s=Student('老李')
print s.score[:5:2]
s[:0]=[100]
print s.score
--->>结果
[10, 12, 14]
[100, 10, 11, 12, 13, 14, 15]

delslice方法,删除指定索引的值

class Student(object):
    def __init__(self,name):
        self.name=name
        self.score=[10,11,12,13,14,15]

    def __getslice__(self,i,j,step):
        return self.score[i,j,step]

    def __setslice__(self, i, j, sequence):
        self.score[i:j]=sequence

    def __delslice__(self, i, j):
        del self.score[i,j]
s=Student('老李')
print s.score[:5:2]
s[:0]=[100]
print s.score
del s.score[0:4]
print s.score
---->>>>结果初始化score[100, 10, 11, 12]这四个值会被删除
[10, 12, 14]
[100, 10, 11, 12, 13, 14, 15]
[13, 14, 15]