Common operations of set in python-Python Tutorial-php.cn

Common operations of set in python

高洛峰

Release： 2017-03-01 14:00:53

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Python's set is similar to other languages. It is an unordered set of non-repeating elements. Its basic functions include relationship testing and elimination of duplicate elements. Set objects also support union, intersection, difference and sysmmetric Mathematical operations such as difference (symmetric difference set)

sets support x in set, len(set), and for x in set. As an unordered collection, sets do not record element positions or insertion points. Therefore, sets do not support indexing, slicing, or other sequence-like operations.

Let’s use a few examples to briefly explain

Common operations 1

In [2]: a = set() 
 
In [3]: a
Out[3]: set()
 
In [4]: type(a)
Out[4]: set
 
In [5]: b = set([1, 3])
 
In [6]: b
Out[6]: {1, 3}
 
In [7]: type(b)
Out[7]: set
 
In [8]: b.update(2)
---------------------------------------------------------------------------
TypeError                 Traceback (most recent call last)
<ipython-input-8-d51e2fe4c50a> in <module>()
----> 1 b.update(2)
 
TypeError: &#39;int&#39; object is not iterable
 
In [9]: b.update({2})
 
In [10]: b
Out[10]: {1, 2, 3}
 
In [11]: b.update([4])
 
In [12]: b
Out[12]: {1, 2, 3, 4}
 
In [13]: a.di
a.difference     a.difference_update a.discard
 
In [13]: a.dif
a.difference     a.difference_update
 
In [13]: a.difference(b)
Out[13]: set()
 
In [14]: a
Out[14]: set()
 
In [15]: b.difference(a)
Out[15]: {1, 2, 3, 4}
 
In [16]:

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Common operations 2

In [16]: a.add({1, 3})
---------------------------------------------------------------------------
TypeError                 Traceback (most recent call last)
<ipython-input-16-98cdf4d0875e> in <module>()
----> 1 a.add({1, 3})
 
TypeError: unhashable type: &#39;set&#39;
 
In [17]: a.add(4)
 
In [18]: a
Out[18]: {4}
 
In [19]: a.issu
a.issubset  a.issuperset
 
In [19]: a.issubset(b)
Out[19]: True
 
In [20]: a.remove(4)
 
In [21]: a
Out[21]: set()
 
In [22]: a.union(b)
Out[22]: {1, 2, 3, 4}
 
In [23]: a
Out[23]: set()
 
In [24]: b
Out[24]: {1, 2, 3, 4}
 
In [25]: b.pop()
Out[25]: 1
 
In [26]: a.copy(b)
---------------------------------------------------------------------------
TypeError                 Traceback (most recent call last)
<ipython-input-26-9e8a5f057ffd> in <module>()
----> 1 a.copy(b)
 
TypeError: copy() takes no arguments (1 given)
 
In [27]: a.copy()
Out[27]: set()
 
In [28]: c = a.copy()
 
In [29]: c
Out[29]: set()
 
In [30]: a
Out[30]: set()
 
In [31]: a.add({234})
---------------------------------------------------------------------------
TypeError                 Traceback (most recent call last)
<ipython-input-31-6073e02d68a9> in <module>()
----> 1 a.add({234})
 
TypeError: unhashable type: &#39;set&#39;
 
In [32]: a.add(234)
 
In [33]: c
Out[33]: set()
 
In [34]: a
Out[34]: {234}

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Common operations 3

In [35]: a.clear()
 
In [36]: a
Out[36]: set()
 
In [39]: a = {1}
 
In [40]: b = {1, 2}
 
In [41]: a.intersection(b)
Out[41]: {1}
 
In [43]: a
Out[43]: {1}
 
In [44]: b = {1, 2, 3}
 
In [45]: a.union(b)
Out[45]: {1, 2, 3}
 
In [45]: a.union(b)
Out[45]: {1, 2, 3}
 
In [46]: a & b
Out[46]: {1}
 
In [47]: a ^ b
Out[47]: {2, 3}
 
In [48]: a - b
Out[48]: set()
 
In [49]: b - a
Out[49]: {2, 3}

In [50]: a > b
Out[50]: False
 
In [51]: b > a
Out[51]: True
 
In [52]: a == b
Out[52]: False
 
In [53]: a != b
Out[53]: True

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