元组类型内置方法

一、元组（tuple）

元组是不可变的列表，即元组的值不可更改，因此元组一般只用于只存不取的需求。也因此元组可以被列表取代掉，所以元组相比较列表使用的很少。元组相比较列表的优点为：列表的值修改后，列表的结构将会发生改变，而元组只需要存储，因此列表在某种程度上而言需要占用更多的内存。

1.1 作用

描述多个爱好，多门课程

1.2 定义方式

在()内可以有多个任意类型的值，逗号分隔元素

hobby_tuple = ('run','read','trip','music')
print(f"hobby_tuple:{hobby_tuple}")
--------------------------------------------------------
hobby_tuple:['run', 'read', 'trip', 'music']

name_str = ('jiayi')  # ()只是普通包含的意思
name_tuple = ('jiayi',)

print(f"type(name_str): {type(name_str)}")
print(f"type(name_tuple): {type(name_tuple)}")
--------------------------------------------------------
type(name_str): <class 'str'>
type(name_tuple): <class 'tuple'>

1.3 内置方法

1.3.1优先掌握

1.按索引取值

hobby_tuple = ('run','read','trip','music')
print(f"hobby_tuple:{hobby_tuple[0]}")
---------------------------------------------------------
hobby_tuple:run

2.切片

hobby_tuple = ('run','read','trip','music')
print(f"hobby_tuple:{hobby_tuple[0:3:2]}")
----------------------------------------------------------
hobby_tuple:('run', 'trip')

3.长度

hobby_tuple = ('run','read','trip','music')
print(f"hobby_tuple:{len(hobby_tuple)}")
-----------------------------------------------------
hobby_tuple:4

4.成员运算

hobby_tuple = ('run','read','trip','music')
print(f"run in hobby_tuple:{'run'in hobby_tuple}")
print(f"run not in hobby_tuple:{'run' not in hobby_tuple}")
---------------------------------------------------------
run in hobby_tuple:True
run not in hobby_tuple:False

5.for循环

hobby_tuple = ('run','read','trip','music')
for i in hobby_tuple:
    print(i)
------------------------------------------------------
run
read
trip
music

6.count()

hobby_tuple = ('run','read','trip','music')
print(f"hobby_tuple.count('run):{hobby_tuple.count('run')}")    #查找run在元组中出现的次数
---------------------------------------------------------
hobby_tuple.count('run):1

7.index()

hobby_tuple = ('run','read','trip','music')
print(f"hobby_tuple.index('run'):{hobby_tuple.index('run')}")  #查找run在元组中第一次出现的位置
---------------------------------------------------------
hobby_tuple.index('run'):0

1.4 有一个值还是多个值

多个值

1.5 有序（索引）or无序（索引）

有序

1.6 可变or不可变

不可变

二、元组和列表的区别

l = ['a','b','c','d']
print(f"l_id:{id(l[0])}")
l[0] = 'A'
print(f"l_id:{id(l[0])}")
-------------------------------------------------------
l_id:2426468149880
l_id:2426469793840

列表可变的原因：索引所对应的值的内存地址是可以变得

元组不可变的原因：索引所对应的值的内存地址是不可变的，也就是说只要索引对应值的内存地址没有改变，那么元组是始终没有改变的。