假設(shè)connectionDetails是Python字典，那么像這樣的重構(gòu)代碼的最佳，最優(yōu)雅，最“ pythonic”的方法是什么？if "host" in connectionDetails: host = connectionDetails["host"]else: host = someDefaultValue
3 回答
慕神8447489
TA貢獻(xiàn)1780條經(jīng)驗(yàn) 獲得超1個贊
像這樣：
host = connectionDetails.get('host', someDefaultValue)
慕運(yùn)維8079593
TA貢獻(xiàn)1876條經(jīng)驗(yàn) 獲得超5個贊
您也可以這樣使用defaultdict：
from collections import defaultdict
a = defaultdict(lambda: "default", key="some_value")
a["blabla"] => "default"
a["key"] => "some_value"
您可以傳遞任何普通函數(shù)而不是lambda：
from collections import defaultdict
def a():
return 4
b = defaultdict(a, key="some_value")
b['absent'] => 4
b['key'] => "some_value"
慕標(biāo)琳琳
TA貢獻(xiàn)1830條經(jīng)驗(yàn) 獲得超9個贊
雖然這.get()是一個很好的習(xí)慣用法，但是它比if/else（比try/except大多數(shù)情況下可以預(yù)期字典中鍵的存在要慢）：
>>> timeit.timeit(setup="d={1:2, 3:4, 5:6, 7:8, 9:0}",
... stmt="try:\n a=d[1]\nexcept KeyError:\n a=10")
0.07691968797894333
>>> timeit.timeit(setup="d={1:2, 3:4, 5:6, 7:8, 9:0}",
... stmt="try:\n a=d[2]\nexcept KeyError:\n a=10")
0.4583777282275605
>>> timeit.timeit(setup="d={1:2, 3:4, 5:6, 7:8, 9:0}",
... stmt="a=d.get(1, 10)")
0.17784020746671558
>>> timeit.timeit(setup="d={1:2, 3:4, 5:6, 7:8, 9:0}",
... stmt="a=d.get(2, 10)")
0.17952161730158878
>>> timeit.timeit(setup="d={1:2, 3:4, 5:6, 7:8, 9:0}",
... stmt="if 1 in d:\n a=d[1]\nelse:\n a=10")
0.10071221458065338
>>> timeit.timeit(setup="d={1:2, 3:4, 5:6, 7:8, 9:0}",
... stmt="if 2 in d:\n a=d[2]\nelse:\n a=10")
0.06966537335119938
添加回答
舉報
0/150
提交
取消