'''列表推導式 & 集合推導式 & 字典推導式'''

列表推導式

list = [x*y for x in range(1,5) if x > 2 for y in range(1,4) if y < 3]

集合推導式

a = {x for x in 'abracadabra' if x not in 'abc'}

字典推導式

#key and value 對換
Dict={"name":"ma jun","age":23,"gender":"boy","job":"sales"}
D = {value:key for key,value in Dict.items()}

#{'ma jun': 'name', 23: 'age', 'boy': 'gender', 'sales': 'job'}

List=["America","China","Russia","England","Korea","India"]
Dict={key:value for value,key in enumerate(List)}

#{'America': 0, 'China': 1, 'Russia': 2, 'England': 3, 'Korea': 4, 'India': 5}

函數

dict.items()

#dict.items()用於遍歷字典
dict = {'Google': 'www.google.com', 'Runoob': 'www.runoob.com', 'taobao': 'www.taobao.com'}
print("result:", dict.items())
print("result: %s"%dict.items())
#for example:
for key,value in dict.items():
    print(key,value)

'''
Google www.google.com
Runoob www.runoob.com
taobao www.taobao.com
'''

enumerate() 函數用於將一個可遍歷的數據對象(如列表、元組或字符串)組合爲一個索引序列，同時列出數據和數據下標，一般用在 for 循環當中。

語法：enumerate(sequence, [start=0])

seq = ['one', 'two', 'three']
for i,value in enumerate(seq):
    print(i,value)

'''
0 one
1 two
2 three
'''