天池龙珠计划 Python训练营
所记录的知识点
- set()
- set(str)
- set 不支持索引访问
- intersection intersection_update
- union
- difference difference_update
- symmetric_difference symmetric_difference_update
- issubset
- issuperset
- isdisjoint
- reversed(seq)
- zip
1、set()
创建空集合，只能使用set()
In [1]: empty_set = set()
In [2]: empty_set
Out[2]: set()
In [3]: {}
Out[3]: {}
In [4]: type({}) # dict!
Out[4]: dict
In [5]: help(set)
Help on class set in module builtins:
class set(object)
| set() -> new empty set object
| set(iterable) -> new set object
|
| Build an unordered collection of unique elements.
|
| Methods defined here:
|
| __and__(self, value, /)
| Return self&value.
|
| __contains__(...)
| x.__contains__(y) <==> y in x.
|
| __eq__(self, value, /)
| Return self==value.
|
| __ge__(self, value, /)
| Return self>=value.
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __gt__(self, value, /)
| Return self>value.
|
| __iand__(self, value, /)
| Return self&=value.
|
| __init__(self, /, *args, **kwargs)
| Initialize self. See help(type(self)) for accurate signature.
|
| __ior__(self, value, /)
| Return self|=value.
|
| __isub__(self, value, /)
| Return self-=value.
|
| __iter__(self, /)
| Implement iter(self).
|
| __ixor__(self, value, /)
| Return self^=value.
|
| __le__(self, value, /)
| Return self<=value.
|
| __len__(self, /)
| Return len(self).
|
| __lt__(self, value, /)
| Return self<value.
|
| __ne__(self, value, /)
| Return self!=value.
|
| __or__(self, value, /)
| Return self|value.
|
| __rand__(self, value, /)
| Return value&self.
|
| __reduce__(...)
| Return state information for pickling.
|
| __repr__(self, /)
| Return repr(self).
|
| __ror__(self, value, /)
| Return value|self.
|
| __rsub__(self, value, /)
| Return value-self.
|
| __rxor__(self, value, /)
| Return value^self.
|
| __sizeof__(...)
| S.__sizeof__() -> size of S in memory, in bytes
|
| __sub__(self, value, /)
| Return self-value.
|
| __xor__(self, value, /)
| Return self^value.
|
| add(...)
| Add an element to a set.
|
| This has no effect if the element is already present.
|
| clear(...)
| Remove all elements from this set.
|
| copy(...)
| Return a shallow copy of a set.
|
| difference(...)
| 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.)
|
| difference_update(...)
| Remove all elements of another set from this set.
|
| discard(...)
| Remove an element from a set if it is a member.
|
| If the element is not a member, do nothing.
|
| intersection(...)
| Return the intersection of two sets as a new set.
|
| (i.e. all elements that are in both sets.)
|
| intersection_update(...)
| Update a set with the intersection of itself and another.
|
| isdisjoint(...)
| Return True if two sets have a null intersection.
|
| issubset(...)
| Report whether another set contains this set.
|
| issuperset(...)
| Report whether this set contains another set.
|
| pop(...)
| Remove and return an arbitrary set element.
| Raises KeyError if the set is empty.
|
| remove(...)
| Remove an element from a set; it must be a member.
|
| If the element is not a member, raise a KeyError.
|
| symmetric_difference(...)
| Return the symmetric difference of two sets as a new set.
|
| (i.e. all elements that are in exactly one of the sets.)
|
| symmetric_difference_update(...)
| Update a set with the symmetric difference of itself and another.
|
| union(...)
| Return the union of sets as a new set.
|
| (i.e. all elements that are in either set.)
|
| update(...)
| Update a set with the union of itself and others.
|
| ----------------------------------------------------------------------
| Static methods defined here:
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
|
| ----------------------------------------------------------------------
| Data and other attributes defined here:
|
| __hash__ = None
2、set(str)
set(str) 可以对字符串中的元素进行去重
In [4]: set("hello world")
Out[4]: {' ', 'd', 'e', 'h', 'l', 'o', 'r', 'w'}
3、set 不支持索引访问
'set' object is not subscriptable
In [1]: set("hello world")
Out[1]: {' ', 'd', 'e', 'h', 'l', 'o', 'r', 'w'}
In [2]: set("hello world")[0]
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-2-9d9ce92dfea5> in <module>
----> 1 set("hello world")[0]
TypeError: 'set' object is not subscriptable
4、intersection intersection_update
集合论中，设A，B是两个集合，由所有属于集合A且属于集合B的元素所组成的集合，叫做集合A与集合B的交集
intersection : 交集，返回一个新的集合
intersection_update : 交集，更新现有的集合
In [4]: set_a = set([1,2,3,4,5])
In [5]: set_b = set([3,4,5,6,7])
In [6]: set_c = set_a.intersection(set_b)
In [7]: set_a
Out[7]: {1, 2, 3, 4, 5}
In [8]: set_b
Out[8]: {3, 4, 5, 6, 7}
In [9]: set_c
Out[9]: {3, 4, 5}
In [10]: help(set().intersection)
Help on built-in function intersection:
intersection(...) method of builtins.set instance
Return the intersection of two sets as a new set.
(i.e. all elements that are in both sets.)
In [11]: set_a
Out[11]: {1, 2, 3, 4, 5}
In [12]: set_b
Out[12]: {3, 4, 5, 6, 7}
In [13]: set_a.intersection_update(set_b)
In [14]: set_a
Out[14]: {3, 4, 5}
In [15]: set_b
Out[15]: {3, 4, 5, 6, 7}
In [16]: help(set().intersection_update)
Help on built-in function intersection_update:
intersection_update(...) method of builtins.set instance
Update a set with the intersection of itself and another.
5、union
给定两个集合A，B，把他们所有的元素合并在一起组成的集合，叫做集合A与集合B的并集
union：并集，返回一个新的集合
In [19]: set_a = set([1,2,3,4,5])
In [20]: set_b = set([3,4,5,6,7])
In [21]: set_a.union(set_b)
Out[21]: {1, 2, 3, 4, 5, 6, 7}
In [22]: help(set().union)
Help on built-in function union:
union(...) method of builtins.set instance
Return the union of sets as a new set.
(i.e. all elements that are in either set.)
6、difference difference_update
设A，B是两个集合，由所有属于A且不属于B的元素组成的集合，叫做集合A减集合B(或集合A与集合B之差)
difference：差集，返回一个新的集合
difference_update： 差集，更新现有的集合
In [24]: set_a = set([1,2,3,4,5])
In [25]: set_b = set([3,4,5,6,7])
In [26]: set_a.difference(set_b)
Out[26]: {1, 2}
In [27]: help(set().difference)
Help on built-in function difference:
difference(...) method of builtins.set instance
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.)
In [28]: set_a = set([1,2,3,4,5])
In [29]: set_b = set([3,4,5,6,7])
In [30]: set_a.difference_update(set_b)
In [31]: set_a
Out[31]: {1, 2}
In [32]: set_b
Out[32]: {3, 4, 5, 6, 7}
In [33]: help(set().difference_update)
Help on built-in function difference_update:
difference_update(...) method of builtins.set instance
Remove all elements of another set from this set.
7、symmetric_difference symmetric_difference_update
对称差集：集合A与集合B中所有不属于A∩B的元素的集合（个人理解：A并B后，再除去A交B的元素）
symmetric_difference：对称差集，返回一个新的集合
symmetric_difference_update：对称差集，更新现有的集合
In [35]: set_a = set([1,2,3,4,5])
In [36]: set_b = set([3,4,5,6,7])
In [37]: set_c = set_a.symmetric_difference(set_b)
In [38]: set_a
Out[38]: {1, 2, 3, 4, 5}
In [39]: set_b
Out[39]: {3, 4, 5, 6, 7}
In [40]: set_c
Out[40]: {1, 2, 6, 7}
In [46]: help(set().symmetric_difference)
Help on built-in function symmetric_difference:
symmetric_difference(...) method of builtins.set instance
Return the symmetric difference of two sets as a new set.
(i.e. all elements that are in exactly one of the sets.)
In [41]: set_a
Out[41]: {1, 2, 3, 4, 5}
In [42]: set_b
Out[42]: {3, 4, 5, 6, 7}
In [43]: set_a.symmetric_difference_update(set_b)
In [44]: set_a
Out[44]: {1, 2, 6, 7}
In [45]: set_b
Out[45]: {3, 4, 5, 6, 7}
In [47]: help(set().symmetric_difference_update)
Help on built-in function symmetric_difference_update:
symmetric_difference_update(...) method of builtins.set instance
Update a set with the symmetric difference of itself and another.
8、issubset
a.issubset(b)：被包含，即 a是b的子集吗？
In [49]: set_a = {1,2,3,4,5,6,7}
In [50]: set_b = {1,2,3,4}
In [51]: set_c = {0,1,2}
In [52]: set_c.issubset(set_a)
Out[52]: False
In [53]: set_b.issubset(set_a)
Out[53]: True
In [54]: set_a.issubset(set_b)
Out[54]: False
In [55]: set_a.issubset(set_c)
Out[55]: False
9、issuperset
a.issuperset(b)：超集，即 a是b的超集吗？
In [57]: set_a = {1,2,3,4,5,6,7}
In [58]: set_b = {1,2,3,4}
In [59]: set_c = {0,1,2}
In [60]: set_a.issuperset(set_b)
Out[60]: True
In [61]: set_a.issuperset(set_c)
Out[61]: False
In [62]: set_b.issuperset(set_a)
Out[62]: False
In [63]: set_c.issuperset(set_a)
Out[63]: False
10、isdisjoint
isdisjoint：判断两个集合是否没有相同元素
In [64]: set_a
Out[64]: {1, 2, 3, 4, 5, 6, 7}
In [65]: set_b
Out[65]: {1, 2, 3, 4}
In [66]: set_c
Out[66]: {0, 1, 2}
In [67]: set_d = {9}
In [68]: set_d.isdisjoint(set_a)
Out[68]: True
In [69]: set_c.isdisjoint(set_a)
Out[69]: False
In [70]: set_b.isdisjoint(set_a)
Out[70]: False
In [71]: set_a.isdisjoint(set_a)
Out[71]: False
11、reversed(seq)
reversed(seq)：返回一个反转的迭代器
In [75]: s = "hello world"
In [76]: iter = reversed(s)
In [77]: iter
Out[77]: <reversed at 0x20a46771df0>
In [78]: type(iter)
Out[78]: reversed
In [79]: next(iter)
Out[79]: 'd'
In [80]: next(iter)
Out[80]: 'l'
In [81]: next(iter)
Out[81]: 'r'
In [82]: next(iter)
Out[82]: 'o'
In [83]: next(iter)
Out[83]: 'w'
In [84]: next(iter)
Out[84]: ' '
In [85]: next(iter)
Out[85]: 'o'
In [86]: next(iter)
Out[86]: 'l'
In [87]: next(iter)
Out[87]: 'l'
In [88]: next(iter)
Out[88]: 'e'
In [89]: next(iter)
Out[89]: 'h'
In [90]: next(iter)
---------------------------------------------------------------------------
StopIteration Traceback (most recent call last)
<ipython-input-90-1a5d8c630f55> in <module>
----> 1 next(iter)
StopIteration:
In [91]: help(reversed)
Help on class reversed in module builtins:
class reversed(object)
| reversed(sequence, /)
|
| Return a reverse iterator over the values of the given sequence.
|
| Methods defined here:
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __iter__(self, /)
| Implement iter(self).
|
| __length_hint__(...)
| Private method returning an estimate of len(list(it)).
|
| __next__(self, /)
| Implement next(self).
|
| __reduce__(...)
| Return state information for pickling.
|
| __setstate__(...)
| Set state information for unpickling.
|
| ----------------------------------------------------------------------
| Static methods defined here:
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
12、zip
zip：打包
zip(*list)：将元祖解压为列表
In [93]: a = [1,2,3]
In [94]: b = [4,5,6]
In [95]: c = [7,8,9,0]
In [96]: zip(a,b)
Out[96]: <zip at 0x20a4693fe40>
In [97]: list(zip(a,b))
Out[97]: [(1, 4), (2, 5), (3, 6)]
In [98]: list(zip(a,c))
Out[98]: [(1, 7), (2, 8), (3, 9)]
In [99]: list(zip(c,a))
Out[99]: [(7, 1), (8, 2), (9, 3)]In [103]: d = [(7, 1), (8, 2), (9, 3)]
In [104]: list(zip(*d))
Out[104]: [(7, 8, 9), (1, 2, 3)]
In [105]: d = [(7, 1, 3), (8, 2,4), (9, 3,5)]
In [106]: list(zip(*d))
Out[106]: [(7, 8, 9), (1, 2, 3), (3, 4, 5)]
In [107]: d = [(7, 1, 3), (8, 2,4), (9, 3,5,6)]
In [108]: list(zip(*d))
Out[108]: [(7, 8, 9), (1, 2, 3), (3, 4, 5)]
In [109]: d = [(7, 1, 3,7), (8, 2,4), (9, 3,5,6)]
In [110]: list(zip(*d))
Out[110]: [(7, 8, 9), (1, 2, 3), (3, 4, 5)]
In [111]: d = [(7, 1, 3,7), (8, 2,4,8,0), (9, 3,5,6)]
In [112]: list(zip(*d))
Out[112]: [(7, 8, 9), (1, 2, 3), (3, 4, 5), (7, 8, 6)]In [116]: help(zip)
Help on class zip in module builtins:
class zip(object)
| zip(*iterables) --> A zip object yielding tuples until an input is exhausted.
|
| >>> list(zip('abcdefg', range(3), range(4)))
| [('a', 0, 0), ('b', 1, 1), ('c', 2, 2)]
|
| The zip object yields n-length tuples, where n is the number of iterables
| passed as positional arguments to zip(). The i-th element in every tuple
| comes from the i-th iterable argument to zip(). This continues until the
| shortest argument is exhausted.
|
| Methods defined here:
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __iter__(self, /)
| Implement iter(self).
|
| __next__(self, /)
| Implement next(self).
|
| __reduce__(...)
| Return state information for pickling.
|
| ----------------------------------------------------------------------
| Static methods defined here:
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
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