1. 集合的特点
① 不同元素组成
>>> num = {1,1,2,3,}
>>> num
{1, 2, 3}
>>> ② 无序
>>> num[2]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'set' object does not support indexing
>>> ③ 集合中的元素必须是不可变类型（数字，字符串，元组）
>>> s = {(1,2,3),3,"dog"}
>>> s
{3, 'dog', (1, 2, 3)}
>>> s = {[1,2,3],3}
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
>>> s = {{'dog':1,'cat':2},3}
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'dict'
>>> 2. 创建一个元组
① 第一种方法是：直接把一大堆元素用大括号{}括起来
>>> s = {"bird","dog","cat"}
>>> s
{'bird', 'dog', 'cat'}② 第二种方法：用set()方法
>>> s = set("hello")
>>> set
<class 'set'>
>>> s
{'e', 'o', 'l', 'h'}
>>>
>>> s = set(["alex","sb"])
>>> s
{'alex', 'sb'}
>>> 3. 常用的方法
① add()：增加一个元素
>>> s = {1,2,3,4,5,6}
>>> s.add("s")
>>> s.add('3')
>>> s.add(3)
>>> s
{1, 2, 3, 4, 5, 6, '3', 's'}② clear()：清除集合内的元素
>>> s.clear()
>>> s
set()
>>> ③ copy()：复制集合
>>> s1 = s.copy()
>>> s1
set()
>>> ④ pop()：随机删除一个元素
>>> s = {1,2,3,4,5,6}
>>> s.pop()
1
>>> s
{2, 3, 4, 5, 6}
>>> ⑤ remove()：指定元素删除，若元素不存在则报错
>>> s = {1,2,3,4,5,6}
>>> s.remove(2)
>>> s
{1, 3, 4, 5, 6}
>>> ⑥ discard()：指定元素删除，若元素不存在不会报错
>>> s = {"sb",2,3,4,(1,2,3)}
>>> s.discard("sb")
>>> s
{2, 3, 4, (1, 2, 3)}
>>> s.discard("girl")
>>> 4. 其他内置方法
>>> dir(set)
['__and__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__iand__', '__init__', '__init_subclass__', '__ior__', '__isub__', '__iter__', '__ixor__', '__le__', '__len__', '__lt__', '__ne__', '__new__', '__or__', '__rand__', '__reduce__', '__reduce_ex__', '__repr__', '__ror__', '__rsub__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__xor__', 'add', 'clear', 'copy', 'difference', 'difference_update', 'discard', 'intersection', 'intersection_update', 'isdisjoint', 'issubset', 'issuperset', 'pop', 'remove', 'symmetric_difference', 'symmetric_difference_update', 'union', 'update']
>>> 详细如下：
class set(object):
"""
set() -> new empty set object
set(iterable) -> new set object
Build an unordered collection of unique elements.
"""
def add(self, *args, **kwargs): # real signature unknown
"""
Add an element to a set.
This has no effect if the element is already present.
"""
pass
def clear(self, *args, **kwargs): # real signature unknown
""" Remove all elements from this set. """
pass
def copy(self, *args, **kwargs): # real signature unknown
""" Return a shallow copy of a set. """
pass
def difference(self, *args, **kwargs): # real signature unknown
"""
相当于s1-s2
Return the difference of two or more sets as a new set.
(i.e. all elements that are in this set but not the others.)
"""
pass
def difference_update(self, *args, **kwargs): # real signature unknown
""" Remove all elements of another set from this set. """
pass
def discard(self, *args, **kwargs): # real signature unknown
"""
与remove功能相同，删除元素不存在时不会抛出异常
Remove an element from a set if it is a member.
If the element is not a member, do nothing.
"""
pass
def intersection(self, *args, **kwargs): # real signature unknown
"""
相当于s1&s2
Return the intersection of two sets as a new set.
(i.e. all elements that are in both sets.)
"""
pass
def intersection_update(self, *args, **kwargs): # real signature unknown
""" Update a set with the intersection of itself and another. """
pass
def isdisjoint(self, *args, **kwargs): # real signature unknown
""" Return True if two sets have a null intersection. """
pass
def issubset(self, *args, **kwargs): # real signature unknown
"""
相当于s1<=s2
Report whether another set contains this set. """
pass
def issuperset(self, *args, **kwargs): # real signature unknown
"""
相当于s1>=s2
Report whether this set contains another set. """
pass
def pop(self, *args, **kwargs): # real signature unknown
"""
Remove and return an arbitrary set element.
Raises KeyError if the set is empty.
"""
pass
def remove(self, *args, **kwargs): # real signature unknown
"""
Remove an element from a set; it must be a member.
If the element is not a member, raise a KeyError.
"""
pass
def symmetric_difference(self, *args, **kwargs): # real signature unknown
"""
相当于s1^s2
Return the symmetric difference of two sets as a new set.
(i.e. all elements that are in exactly one of the sets.)
"""
pass
def symmetric_difference_update(self, *args, **kwargs): # real signature unknown
""" Update a set with the symmetric difference of itself and another. """
pass
def union(self, *args, **kwargs): # real signature unknown
"""
相当于s1|s2
Return the union of sets as a new set.
(i.e. all elements that are in either set.)
"""
pass
def update(self, *args, **kwargs): # real signature unknown
""" Update a set with the union of itself and others. """
pass
def __and__(self, *args, **kwargs): # real signature unknown
""" Return self&value. """
pass
def __contains__(self, y): # real signature unknown; restored from __doc__
""" x.__contains__(y) <==> y in x. """
pass
def __eq__(self, *args, **kwargs): # real signature unknown
""" Return self==value. """
pass
def __getattribute__(self, *args, **kwargs): # real signature unknown
""" Return getattr(self, name). """
pass
def __ge__(self, *args, **kwargs): # real signature unknown
""" Return self>=value. """
pass
def __gt__(self, *args, **kwargs): # real signature unknown
""" Return self>value. """
pass
def __iand__(self, *args, **kwargs): # real signature unknown
""" Return self&=value. """
pass
def __init__(self, seq=()): # known special case of set.__init__
"""
set() -> new empty set object
set(iterable) -> new set object
Build an unordered collection of unique elements.
# (copied from class doc)
"""
pass
def __ior__(self, *args, **kwargs): # real signature unknown
""" Return self|=value. """
pass
def __isub__(self, *args, **kwargs): # real signature unknown
""" Return self-=value. """
pass
def __iter__(self, *args, **kwargs): # real signature unknown
""" Implement iter(self). """
pass
def __ixor__(self, *args, **kwargs): # real signature unknown
""" Return self^=value. """
pass
def __len__(self, *args, **kwargs): # real signature unknown
""" Return len(self). """
pass
def __le__(self, *args, **kwargs): # real signature unknown
""" Return self<=value. """
pass
def __lt__(self, *args, **kwargs): # real signature unknown
""" Return self<value. """
pass
@staticmethod # known case of __new__
def __new__(*args, **kwargs): # real signature unknown
""" Create and return a new object. See help(type) for accurate signature. """
pass
def __ne__(self, *args, **kwargs): # real signature unknown
""" Return self!=value. """
pass
def __or__(self, *args, **kwargs): # real signature unknown
""" Return self|value. """
pass
def __rand__(self, *args, **kwargs): # real signature unknown
""" Return value&self. """
pass
def __reduce__(self, *args, **kwargs): # real signature unknown
""" Return state information for pickling. """
pass
def __repr__(self, *args, **kwargs): # real signature unknown
""" Return repr(self). """
pass
def __ror__(self, *args, **kwargs): # real signature unknown
""" Return value|self. """
pass
def __rsub__(self, *args, **kwargs): # real signature unknown
""" Return value-self. """
pass
def __rxor__(self, *args, **kwargs): # real signature unknown
""" Return value^self. """
pass
def __sizeof__(self): # real signature unknown; restored from __doc__
""" S.__sizeof__() -> size of S in memory, in bytes """
pass
def __sub__(self, *args, **kwargs): # real signature unknown
""" Return self-value. """
pass
def __xor__(self, *args, **kwargs): # real signature unknown
""" Return self^value. """
pass
__hash__ = None集合的关系运算
① in /not in
>>> s1 = {1,2,3,4,5,6}
>>> 1 in s1
True
>>> 7 in s1
False
>>> 2 not in s1
False
>>> 7 not in s1
True
>>> ② 关系运算
1.交集-----intersection 符号 &
python_l = ['鸡总','老司机','游总','老王']
linux_l = ['鸡总','老王','容哥','大毛']
python_s = set(python_l)
linux_s = set(linux_l)
print(python_s,linux_s)
print(python_s.intersection(linux_s)) #求交集
print(python_s&linux_s) # &作用于intersection一样
打印:
{'游总', '老司机', '老王', '鸡总'} {'大毛', '容哥', '老王', '鸡总'}
{'老王', '鸡总'}
{'老王', '鸡总'}2.并集----- union 符号 |
print(python_s.union(linux_s))
print(python_s|linux_s)
打印:
{'容哥', '老司机', '大毛', '游总', '老王', '鸡总'}
{'容哥', '老司机', '大毛', '游总', '老王', '鸡总'}print('差集',python_s.difference(linux_s))
print('差集',linux_s.difference(python_s))
print("差集",python_s - linux_s)
print("差集",linux_s - python_s)
打印:
差集 {'游总', '老司机'}
差集 {'容哥', '大毛'}
差集 {'游总', '老司机'}
差集 {'容哥', '大毛'}4.交叉补集 symmetric_difference 符号 ^
print('交叉补集',python_s.symmetric_difference(linux_s))
print('交叉补集',linux_s.symmetric_difference(python_s))
print('交叉补集',python_s^linux_s)
print('交叉补集',linux_s^python_s)
打印：
交叉补集 {'容哥', '大毛', '游总', '老司机'}
交叉补集 {'游总', '容哥', '大毛', '老司机'}
交叉补集 {'容哥', '大毛', '游总', '老司机'}
交叉补集 {'游总', '容哥', '大毛', '老司机'}5.difference_update
python_s = python_s - linux_s
print(python_s)
python_s = python_s.difference(linux_s)
print(python_s)
#difference_update相当于python_s = python_s.difference(linux_s)
python_s.difference_update(linux_s)
print(python_s)
打印：
{'老司机', '游总'}
{'游总', '老司机'}
{'游总', '老司机'}6.intersection_update 更新intersection后的集合
python_s = python_s.intersection(linux_s)
print(python_s)
python_s.intersection_update(linux_s)
print(python_s)
打印：
{'鸡总', '老王'}
{'鸡总', '老王'}7.symmetric_difference_update
python_s.symmetric_difference_update(linux_s)
print(python_s)
打印：
{'容哥', '大毛', '游总', '老司机'}s1 = {1,2}
s2 = {3,5}
print(s1.isdisjoint(s2))
打印：
True9.issubset 一个集合是例外一个集合的子集，若为真，则返回True
s1 = {1,2}
s2 = {1,2,3,4}
print(s1.issubset(s2))
print(s2.issubset(s1))
打印：
True
False
10.update 更新集合多个值，用于增加集合元素 参数只能是可迭代对象，与add()不同
s1 = {1,2}
s2 = {1,2,3,4}
s1.update(s2)
print(s1)
s1.update((5,6))
print(s1)
s1.update([7,8])
print(s1)
s1.update('hello')
print(s1)
打印：
{1,2,3,4}
{1, 2, 3, 4, 5, 6}
{1, 2, 3, 4, 5, 6, 7, 8}
{'o', 1, 2, 3, 4, 5, 6, 7, 8, 'l', 'h', 'e'}5.不可变集合
有些时候我们希望集合中的数据是稳定的，像元组一样不能随意修改删除集合中的元素，我们可以定义不可变集合，使用frozenset()函数
>>> set_test = set('hello')
>>> set_test
{'e', 'h', 'o', 'l'}
>>> s1 = frozenset(set_test)
>>> print(s1)
frozenset({'e', 'h', 'o', 'l'})>>> s1.add('p')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'frozenset' object has no attribute 'add'
>>> s1.pop()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'frozenset' object has no attribute 'pop'作业题：
1.有列表l=['a','b',1,'a','a']，列表元素均为可hash类型，去重，得到新列表,且新列表无需保持列表原来的顺序
l=['a','b',1,'a','a']
print(set(l))l=['a','b',1,'a','a']
l1 = []
for i in l:
if i not in l1:
l1.append(i)
print(l1)l=['a','b',1,'a','a']
s = set()
l1 = []
for i in l:
if i not in s:
s.add(i)
l1.append(i)
print(l1)l=[
{'name':'egon','age':18,'sex':'male'},
{'name':'alex','age':73,'sex':'male'},
{'name':'egon','age':20,'sex':'female'},
{'name':'egon','age':18,'sex':'male'},
{'name':'egon','age':18,'sex':'male'},
]
l=[
{'name':'egon','age':18,'sex':'male'},
{'name':'alex','age':73,'sex':'male'},
{'name':'egon','age':20,'sex':'female'},
{'name':'egon','age':18,'sex':'male'},
{'name':'egon','age':18,'sex':'male'},
]
s = set()
l1 = []
for i in l:
item = (i['name'],i['age'],i['sex'])
if item not in s:
s.add(item)
l1.append(item)
print(l1)