PYTHON 入门之 分片
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分片(slice)
给出 《python基础教程》关于分片的描述:与使用索引来访问单个元素类似,可以使用分片操作来访问一定范围内的元素。分片通过冒号隔开的两个索引来实现。
Python 3语言:高亮代码由发芽网提供
#join()
>>> seq1 = ['hello','good','boy','!']
>>> print (''.join(seq1))
hello good boy !
>>> print(':'.join(seq1))
hello:good:boy:!
#删除元素
>>> numbers = [1,2,3,4,5]
>>> del numbers[2:4]
>>> print(numbers)
[1,2,5]
>>> numbers = [1,2,3,4,5]
>>> numbers[2:4]=[]
>>> print(numbers)
[1,2,5]
#分片赋值
>>> a = ['a','b','c','d','e','f','g']
>>> a[2:5] = ['1','2']
>>> print(a)
['a','b','1','2','f','g']
>>> a = ['a','b','c','d','e','f','g']
>>> a[2:5] = ['1','2','3','4']
>>> print(a)
['a','b','1','2','3','4','f','g']
#离散
>>> a = [1,2,3,4,5]
>>> a[1:4:2] = [100,100] #步进为2:赋值的个数(2)必须等于替换的元素个数(2)
>>> print(a)
[1,100,3,100,5]
>>> a = [1,2,3,4,5]
>>> a[1:4:1]=[100,100] #步进为1:赋值的个数(2)必须小于等于替换的元素个数(3)
>>> print(a)
[1,100,100,5]
>>> a = [1,2,3,4,5]
>>> a[1:4]=[100,100,100,100,100] #不指明步进可变长
>>> print(a)
[1,100,100,100,100,100,5]
#插入
>>> a = [1,2,3,4,5]
>>> a[1:1]=[100,100,100,100,100] # a[1:1:1] =也可以,a[1:1:2] = 错误. \
#插入时步进1或不要步进可以,大于1不行
>>> print(a)
[1,100,100,100,100,100,2,3,4,5]
>>> seq1 = ['hello','good','boy','!']
>>> print (''.join(seq1))
hello good boy !
>>> print(':'.join(seq1))
hello:good:boy:!
#删除元素
>>> numbers = [1,2,3,4,5]
>>> del numbers[2:4]
>>> print(numbers)
[1,2,5]
>>> numbers = [1,2,3,4,5]
>>> numbers[2:4]=[]
>>> print(numbers)
[1,2,5]
#分片赋值
>>> a = ['a','b','c','d','e','f','g']
>>> a[2:5] = ['1','2']
>>> print(a)
['a','b','1','2','f','g']
>>> a = ['a','b','c','d','e','f','g']
>>> a[2:5] = ['1','2','3','4']
>>> print(a)
['a','b','1','2','3','4','f','g']
#离散
>>> a = [1,2,3,4,5]
>>> a[1:4:2] = [100,100] #步进为2:赋值的个数(2)必须等于替换的元素个数(2)
>>> print(a)
[1,100,3,100,5]
>>> a = [1,2,3,4,5]
>>> a[1:4:1]=[100,100] #步进为1:赋值的个数(2)必须小于等于替换的元素个数(3)
>>> print(a)
[1,100,100,5]
>>> a = [1,2,3,4,5]
>>> a[1:4]=[100,100,100,100,100] #不指明步进可变长
>>> print(a)
[1,100,100,100,100,100,5]
#插入
>>> a = [1,2,3,4,5]
>>> a[1:1]=[100,100,100,100,100] # a[1:1:1] =也可以,a[1:1:2] = 错误. \
>>> print(a)
[1,100,100,100,100,100,2,3,4,5]
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