Lesson 2#04 元组

元组，又称为只读列表

#小括号是元组( )
#中括号是列表[ ]
#大括号是字典{ }
names = ("suyp","lirs","liuzhen","machao")

特性：元组本身不可变，如果元组中包含其他可变元素，这些元素是可变改变的

names = ("suyp","lirs","liuzhen","machao",["zhoubin","wangcc"])
names[0] = "SUYP"
#>>>执行结果：
>>>TypeError: 'tuple' object does not support item assignment 
#元组类型不支持项赋值

names = ("suyp","lirs","liuzhen","machao",["zhoubin","wangcc"])
names[4][0] = "ZHOUBIN"
print(names[4][0])
# >>>执行结果：
>>>ZHOUBIN
#如果元组内有可元素，这些可变元素的值是可以修改的

功能：

index

names = ("suyp","lirs","liuzhen","machao",["zhoubin","wangcc"])
print(names.index("suyp"))
# >>>执行结果：
>>>0
#元组支持index方法，可以快速输出对应索引

count

names = ("suyp","lirs","liuzhen","machao",["zhoubin","wangcc"])
print(names.count("suyp"))
# >>>执行结果：
>>>1
#元组支持.count方法，支持元素计数

切片

names = ("suyp","lirs","liuzhen","machao",["zhoubin","wangcc"])
print(names[0:4])
# >>>执行结果：
>>>('suyp', 'lirs', 'liuzhen', 'machao')
#元组支持切片输出，同列表，顾头不顾尾

使用场景：

显示的告知别人或自己，此处数据定义为不可修改

数据库连接配置信息等