# d.Python - 基本資料結構(Set)、字典(Dict)

###### tags: `Python`

## 1.集合(Set)

* <font color="#0080FF">**重複的資料會被自動刪除**</font>

x = {1,2,1,2,1,2,1,2}
print(x)

>```{1, 2}```
##
* <font color="#0080FF">**邏輯運算**</font>

x = {1,2,3,6}
y = set([1,7,8,9])

print(x | y) #聯集(OR)
print(x & y) #交集(AND)
print(x ^ y) #對稱差(XOR)

> ```{1, 2, 3, 6, 7, 8, 9}```</br>
> ```{1}```</br>
> ```{2, 3, 6, 7, 8, 9}```

## 2.集合常用方法(method)與操作

* <font color="#0080FF">**Set 無序的資料型態 - 不支援切片、索引及「順序相關」的「+」及「*」操作**</font>

x = set([1,2,3,1,3,5])
print(x)

x.add(6) #新增元素
print(x)

x.remove(5) #刪除元素
print(x)

print(1 in x)
print(4 in x)

> ```{1, 2, 3, 5}```</br>
> ```{1, 2, 3, 5, 6}```</br>
> ```{1, 2, 3, 6}```</br>
> ```True```</br>
> ```False```
##
* <font color="#0080FF">**frozenset()**</font>

x = set([1,2,3,1,3,5])
z = frozenset(x)
print(z)

z.add(6) #frozenset為不可變動型別，產生錯誤
x.add(z) #set裡面只可存放不可變動物件(如frozenset)
print(x)

> ```frozenset({1, 2, 3, 5})```</br>
> ```AttributeError: 'frozenset' object has no attribute 'add'```</br>
> ```{1, 2, 3, 5, frozenset({1, 2, 3, 5})}```

## 3.字典(Dict)

> <font color="#EA0000">**字典會自動依照索引排序 (如A-Z)**</font>

* <font color="#0080FF">**dict 和 set 的宣告**</font>

x = {} #建立空字典
print(type(x))

x = {1} #要建立'set'一定要先有值
print(type(x))

> ```<class 'dict'>```</br>
> ```<class 'set'>```
##
* <font color="#0080FF">**del 來刪除字典中項目**</font>

store = {'apple':25,'banana':30,'orange':40,'tomato':50}
del store['tomato']
store

> ```{'apple': 25, 'banana': 30, 'orange': 40}```
##
* <font color="#0080FF">**get() 和 setdefault()**</font>

#<!>若找不到值，則回傳第二個參數設定(無第二參數則結束)
store.get('lemon','No translation') 

store.setdefault('lemon','No translation') #若該key不存在，則新增key-value
store

store.setdefault('banana','No translation') #若該key已存在，則不變
store

> ```'No translation'```</br>
> ```{'apple': 25, 'banana': 30, 'lemon': 'No translation', 'orange': 40}```</br>
> ```{'apple': 25, 'banana': 30, 'lemon': 'No translation', 'orange': 40}```
##
* <font color="#0080FF">**copy() 取得字典的副本**</font>

a = {0:'zero',1:'one'}
b = a.copy()
b

> ```{0: 'zero', 1: 'one'}```</br>
##
* <font color="#0080FF">**update() 兩個字典的合併**</font>

up = {1:'ONE',2:'TWO'}
down = {0:'zero',1:"one"}

down.update(up)
down

> ```{0: 'zero', 1: 'ONE', 2: 'TWO'}```
##
* <font color="#0080FF">**<!>以字典作為快取**</font>

sole_cache = {}  #快取
def sole(m,n,t):
  if(m,n,t) in sole_cache:
    #如果字典裡已經有此鍵
    return sole_cache[(m,n,t)]
  else:
    #否則...對(m,n,t)做一些計算
    result = m * n * t
    sole_cache[(m,n,t)] = result
    return result
    
sole(5,5,5)
sole_cache

> ```125```</br>
> ```{(5, 5, 5): 125}```

## 時間戳記

> [name=ZEOxO][time=Mon, Aug 24, 2020 15:46 PM][color=#907bf7]