# set #
python set , ,
set dict set value
## 1set ##
set list
```python
set1=set([123,456,789])
print(set1)
```
```
{456, 123, 789}
```
`[123,456,789]` list `{456, 123, 789}` set 456, 123, 789 3 list set
tuple () list () , dict () dict dict key-value set key
dict key key-value set
```python
set1=set([123,456,789,123,123])
print(set1)
```
```
{456, 123, 789}
```
## 2set ##
add(key) set
```python
set1=set([123,456,789])
print(set1)
set1.add(100)
print(set1)
set1.add(100)
print(set1)
```
```
{456, 123, 789}
{456, 123, 100, 789}
{456, 123, 100, 789}
```
## 3set ##
remove(key) set
```python
set1=set([123,456,789])
print(set1)
set1.remove(456)
print(set1)
```
```
{456, 123, 789}
{123, 789}
```
## 4set ##
set set union(), intersection(), difference()
- Union
- Intersection
- Difference
```python
set1=set('hello')
set2=set(['p','y','y','h','o','n'])
print(set1)
print(set2)
# ( set )
set3=set1 & set2
print('\n set3:')
print(set3)
# set
set4=set1 | set2
print('\n set4:')
print(set4)
#
set5=set1 - set2
set6=set2 - set1
print('\n set5:')
print(set5)
print('\n set6:')
print( set6)
# hash set
list1 = [111,222,333,444,111,222,333,444,555,666]
set7=set(list1)
print('\n set7:')
print(set7)
```
```
{'h', 'l', 'e', 'o'}
{'h', 'n', 'o', 'y', 'p'}
set3:
{'h', 'o'}
set4:
{'h', 'p', 'n', 'e', 'o', 'y', 'l'}
set5:
{'l', 'e'}
set6:
{'p', 'y', 'n'}
set7:
{555, 333, 111, 666, 444, 222}
```
## 5 set ##
set Python
### 1 ###
`[x * x for x in range(5)]` set
```python
# 1 10
squares = {x * x for x in range(1, 11) if x % 2 == 0}
print(squares)
```
```
{64, 4, 36, 100, 16}
```
`set()`
```python
orders = [
{'user': '', 'amount': 100},
{'user': '', 'amount': 200},
{'user': '', 'amount': 50},
{'user': '', 'amount': 300},
]
users = {order['user'] for order in orders}
print(users)
```
```
{'', '', ''}
```
set `add`
### 2frozenset set ###
set `add` `remove` dict key set
`frozenset`
```python
fs = frozenset([1, 2, 3])
print(fs)
#
print(fs & frozenset([2, 3, 4]))
# dict key
config = {frozenset(['admin', 'editor']): ''}
print(config[frozenset(['editor', 'admin'])])
```
```
frozenset({1, 2, 3})
frozenset({2, 3})
```
`frozenset(['admin', 'editor'])` `frozenset(['editor', 'admin'])` set key
### 3 set list ###
`x in collection`
* `collection` list O(n)
* `collection` set dict O(1)
list set
```python
# 10
names_list = [f'user_{i}' for i in range(100000)]
names_set = set(names_list)
#
print('user_99999' in names_list)
print('user_99999' in names_set)
```
```
True
True
```
set in set