python 容器
PYTHON 容器1 set
容器里边的值是唯一,相同的值只能存在一个，不会出现数据重复的问题。
set的访问速度快
1 新建一个set
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'''
建立一个空的set
'''
theList = set() ==> set()
'''
使用个迭代的对象建立一个set
'''
theList = set() ==> {1,2,3}
2 增加一个元素
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'''
增加一个元素
'''
theSet = set() ==> set()
theSet.add(1) ==> {1}
theSet.add('2') ==>{1,'2'}
3 清空set
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'''
清空集合
'''
theSet = set() ==> set()
theSet.add(1) ==>{1}
theSet.add('2') ==>{1,'2'}
theSet.clear() ==> set()
4 复制set
copy()
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'''
复制集合
'''
firstSet = set() ==> set()
firstSet.add('1') ==> {'1'}
firstSet.add('2') ==> {'1','2'}
secondSet = first.copy() ==> {'1','2'}
secondSet.add('3') ==> {'1','2','3'}
print(firstSet) ==> {'1','2'}
5 返回一个差集
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'''
返回一个差值 difference 方法
'''
a = set() ==> a = 1,2,3,4}
b = set() ==> b ={2,3}
c = set() ==> c = {4}
d = a.difference(b) ==> d = {1,4} , a = {1,2,3,4}
e = a.defference(b,c) ==> e = {1} , a = {1,2,3,4}
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'''
返回一个差值 difference_update 方法
'''
a = set() ==> a = {1,2,3,4}
b = set() ==> b = {4}
c = a.difference_update(b) ==> c = None a = {1,2,3}
6 删除一个元素
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'''
删除一个元素discard方法
'''
a = set() ==> a = {1,2,3,4}
b = a.discard(4) ==> b = None a = {1,2,3}
a.discard(4) ==> a = {1,2,3}
discard 方法正常返回，没有报错
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'''
删除一个元素 remove 方法
'''
a = set() ==> a={1,2,3,4}
a.remove(4) ==> a={1,2,3}
a.remove(4) ==> 抛出keyerror异常
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7 合并两个集合
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'''
返回交集 intersection方法
'''
a = set() ==> a = {1,2,,3,4}
b = set() ==> b = {4}
c = a.intersection(b) ==> c = {4} , a = {1,2,3,4}
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'''
返回交集 intersection_update方法
'''
a = set() ==> a = {1,2,,3,4}
b = set() ==> b = {4}
c = a.intersection_update(b) ==> c = None , a = {4}
8 判断是否有交集
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'''
判断是否有交集 isdisjoin 有交集返回False 无交集返回True
'''
a = set() ==> a={1,2,3,4}
b = set() ==> b={4}
c = set() ==> c={5}
a.isdisjoin(b) ==> False
a.isdisjoin(c) ==> True
9 判断是否是子字串
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'''
判断字符串是不是其他集合的子集 issubset
'''
a = set() ==> a = {1,2,3,4}
b = set()==> b = {1,2,3,4,5}
c = set({0,1}) ==> c = {0,1}
a.issubset(b) ==> True
a.issubset(c) ==> False
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'''
判断其他集合是不是自己的子集 issuperset
'''
a = set() ==> a = {1,2,3,4}
b = set() ==> b = {2,3}
c = set({0,1}) ==> c = {0,1}
a.issuperset(b) ==> True
a.issuperset(c) ==> False
10 返回一个值
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'''
返回一个值
'''
theSet = set() ==> a = {1,2,3,4}
b = theSet.pop() ==> b = 1 , a = {2,3,4}
theSet.pop() ==> 2 , a = {3,4}
theSet.pop() ==> 3 , a = {4}
theSet.pop() ==> 4 , a = {}
theSet.pop() ==> 抛出异常keyerryr
2 计数器
是对字典的补充，作用是统计对象出现的次数
1 创建计数器
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'''
创建计数器
'''
from collections import Counter
c = Counter() ==> Counter()
c = Counter("abcdea") ==> Counter({'a': 2, 'd': 1, 'e': 1, 'b': 1, 'c': 1})
c = Counter({'red': 4, 'blue': 2})==> Counter({'red': 4, 'blue': 2})
c = Counter(cats=4, dogs=8) ==> Counter({'dogs': 8, 'cats': 4})
2 取元素
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'''
获取元素
'''
fromn collections import Counter
c = Counter("who am i") ==> Counter({' ': 2, 'o': 1, 'm': 1, 'i': 1, 'h': 1, 'w': 1, 'a': 1})
list(c.elements()) ==> [' ', ' ', 'o', 'm', 'i', 'h', 'w', 'a']
3 有序字典
有序字典在普通字典的基础上在后台对key进行了排序的操作
4 默认字典
使用了默认字典后，可以在关键字不包含在字典的情况下向字典赋值
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from collections import defalutdict
d = defaultdict(list)
d["first"].append(1) ==> efaultdict(<class 'list'>, {'first': })
5 可命名元祖
增加元祖的访问方法。以前只能使用索引访问，使用可命名元祖后，可以使用名字来访问.数据可以以访问，不可以修改，好像普通的元祖一样
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from collections import namedtuple
Mytupleclass = namedtuple("point",["x","y"])
point = Mytupleclass(11,22)
point.x ==> 11
point.y ==>12
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