Set

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An unorder collection of a unquie object. No duplicate value.
不可以有重複的直，一般都是用在帳號上面。

Create set

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my_set= {1,2,3,4,5}
print(my_set)

output:

{1, 2, 3, 4, 5}

如果加重複會用最前面的

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my_set= {1,2,3,4,5,5}
print(my_set)

output:

{1, 2, 3, 4, 5}

adding set

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my_set= {1,2,3,4,5,5}
my_set.add(100)
my_set.add(2)
print(my_set)

output

‘{1, 2, 3, 4, 5, 100}`

上面會看到2不會被加進去，因為他已經存在。

list to set

如果一把list不要重複，我們就要用到set ，會把重複的直移除。convert list to set, and remove duplicate value 

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my_list= [1, 2, 3, 4, 5, 5, 100]
print(set(my_list))

output:

{1, 2, 3, 4, 5, 100}

basic method

  • get value取直
    set don’t support index，set 不支援 索引取直。

print(my_set[0]) # will be error

我們需要取直，就要把直放進去如:

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my_set= {1,2,3,4,5,5}
print(1 in my_set) #true

  • len()

    print(len(my_set)) #5

  • convert to list

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    my_set= {1,2,3,4,5,5}
    print(list(my_set)) #[1, 2, 3, 4, 5]

  • copy() and clear()

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    my_set= {1,2,3,4,5,5}
    new_set= my_set.copy()
    my_set.clear()
    print(my_set)
    print(new_set)

    output:

    set()
    {1, 2, 3, 4, 5}

advance method

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my_set={1,2,3,4,5}
your_set={4,5,6,7,8,9}

  • difference() 只告訴你不同的，但會保留

    print(my_set.difference(your_set)) #{1, 2, 3}

  • discard()

    print(my_set.discard(5))
    print(my_set)

    output:
    {1, 2, 3, 4}

  • difference_update() 把相同的移除，只保留不同的。他會修改

    my_set.difference_update(your_set)
    print(my_set)

    output:
    #{1, 2, 3}

  • intersection() something in common

    print(my_set.intersection(your_set)) #{4, 5}

of shorthand

print(my_set & your_set) #{4, 5}

  • isdisjoint() something not in common
    print(my_set.isdisjoint(your_set)) #false

if we use like this:

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my_set={1,2,3}
your_set={4,5,6,7,8,9}
print(my_set.isdisjoint(your_set)) #True
  • union() 合併一樣的移除重複

    print(my_set.union(your_set))

or shorthand

print(my_set| your_set)

output:
{1, 2, 3, 4, 5, 6, 7, 8, 9}`

  • issubset()

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    my_set={4,5}
    your_set={4,5,6,7,8,9,10}
    print(my_set.issubset(your_set)) # true

    my_set is a subset of your_set。my_set在your_set裡面，因此就會true

  • issuperset()

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    my_set={4,5}
    your_set={4,5,6,7,8,9,10}
    print(your_set.issuperset(my_set)) # true 
    print(my_set.issubset(your_set)) # true