一、元组类型内置方法(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。但是目前工业上内存已经不是问题了,所以工业上元组一般不会使用。
1.用途:多个装备、多个爱好、多门课程,甚至是多个女朋友
2.定义:在()内可以有多个任意类型的值,逗号分隔元素
# my_girl_friend = tuple(('jason','tank','sean'))
my_girl_friend = ('jason', 'tank', 'sean')
print(f"my_girl_friend: {my_girl_friend}")
my_girl_friend: ('jason', 'tank', 'sean')
name_str = ('egon') # ()只是普通包含的意思
name_tuple = ('egon',)
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'>
3.常用操作+内置方法:常用操作和内置方法:
(1 优先掌握(*)
- 索引取值
- 切片(顾头不顾尾,步长)
- 长度len
- 成员运算in和not in
- 循环
- count
- index
①.索引取值
# tuple之索引取值
name_tuple = ('nick', 'jason', 'tank', 'sean')
# name_tuple[0] = 'nick handsom' # 报错
print(f"name_tuple[0]: {name_tuple[0]}")
name_tuple[0]: nick
②.切片(顾头不顾尾,步长)
# tuple之切片
name_tuple = ('nick', 'jason', 'tank', 'sean')
print(f"name_tuple[1:3:2]: {name_tuple[1:3:2]}")
name_tuple[1:3:2]: ('jason',)
③.长度
# tuple之长度
name_tuple = ('nick', 'jason', 'tank', 'sean')
print(f"len(name_tuple): {len(name_tuple)}")
len(name_tuple): 4
④.成员运算
# tuple之成员运算
name_tuple = ('nick', 'jason', 'tank', 'sean')
print(f"'nick' in name_tuple: {'nick' in name_tuple}")
'nick' in name_tuple: True
⑤.循环
# tuple之循环
name_tuple = ('nick', 'jason', 'tank', 'sean')
for name in name_tuple:
print(name)
nick
jason
tank
sean
⑥.count()
# tuple之count()
name_tuple = ('nick', 'jason', 'tank', 'sean')
print(f"name_tuple.count('nick'): {name_tuple.count('nick')}")
name_tuple.count('nick'): 1
⑦.index()
# tuple之index()
name_tuple = ('nick', 'jason', 'tank', 'sean')
print(f"name_tuple.index('nick'): {name_tuple.index('nick')}")
name_tuple.index('nick'): 0
4.存一个值or多个值:多个值
5.有序or无序:有序
name_tuple = ('nick',)
print(f'first:{id(name_tuple)}')
first:4394454152
6.可变or不可变:不可变数据类型
二、元组和列表的区别
l = ['a', 'b', 'c']
print(f"id(l[0]): {id(l[0])}")
l[0] = 'A'
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print(f"id(l[0]): {id(l[0])}")
id(l[0]): 4357367208
id(l[0]): 4357775176
列表可变的原因是:索引所对应的值的内存地址是可以改变的
元组不可变得原因是:索引所对应的值的内存地址是不可以改变的,或者反过来说,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。
t1 = (['a', 'b', 'c'], 'wc', 'office')
print(f"id(t1[0]): {id(t1[0])}")
print(f"id(t1[1]): {id(t1[1])}")
print(f"id(t1[2]): {id(t1[2])}")
t1[0][0] = 'A'
print(f"t1[0][0]: {t1[0][0]}")
print(f"id(t1[0]): {id(t1[0])}")
print(f"t1: {t1}")
id(t1[0]): 4394709960
id(t1[1]): 4374626968
id(t1[2]): 4394453568
t1[0][0]: A
id(t1[0]): 4394709960
t1: (['A', 'b', 'c'], 'wc', 'office')