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什么是元组
Python内置的数据结构之一,是一个不可变序列
元组的数据类型为tuple
可变序列与不可变序列
* 不可变序列:字符串、元组
* 不可变序列:没有增,删,改,的操作
* 可变序列:列表,字典
* 可变序列:可以对序列进行增、删、改操作,对象地址不发生更改
元组的创建方式
直接小括号
a=('python','hello',90) #小括号也可以省略 a='python','hello',90
使用内置函数tuple()
a=tuple(('python','hello',90))
只包含一个元素的元组需要用括号和逗号
a=(10,)
空元组
a=() a2=tuple()
元组的查询操作
tup=(1,2,3,4,5) print(tup(0)) #返回值是1 print(tup(1)) #返回值是2
为什么要将元组设计为不可变序列
一旦创建了不可变类型对象,对象内部的所有数据就不能被修改了
在多任务环境下,同时操作对象时不需要加锁
因此,在程序中尽量使用不可变序列
注意事项
* 元组中存储的是对象的引用
* 如果元组中对象本身是不可变对象,则不能再引用其他对象
* 如果元组中的对象是可变对象,则可变对象的引用不允许改变,但数据可以改变
元组是不允许修改元素的
由于[20,30]是列表,列表是可变序列,所有可以向列表中添加元素,而列表的内存地址不变
元组的遍历
元组是可迭代对象,所以可以使用for...in进行遍历
a=tuple(('python','hello','90')) for b in a: print(b)
总结