Python 3 Grammar Note (4): Collection

The collection of Python is not equal to the collection of other languages in a broad sense. Strictly speaking, a list is more like a collection, where set set is an unordered collection of non-repeating elements.

* Can be understood as, there is no value only the dictionary of keys. A dictionary of primitive form.

1 Creating a Collection

A_set = set ()             #空集合a_set = {-)

To create a collection with list:

A_set = Set ([Up, "ABC", 4])

2 Modifying a collection element

A_set.add (single Element) a_set.update (single or multiple elements or collections)  #这里可以是集合, or it can be a repeating element in the list collection, and does not increase.

　　

3 删除集合元素

A_set.discard (single Element)      #删除不存在的元素, no effect A_set.remove (single element)       #删除不存在的元素, throws Exception A_set.pop () A_set.clear ()

　　

4 集合操作 

A_set.union (B_set)   #并集a_set. Intersection (B_set)   #交集a_set. Difference (b_set)   #差集a_set. Issubset (b_ Set)   #检测子集

　　

5 布尔检测

• Set () represents an empty collection, false

• Non-empty collection, True

Python 3 Grammar Note (4): Collection