01-20 96—100

96、選擇輸出結果

def doff(arg1, *args):
		print(type(args))
		
doff("applea", "bananas", "cherry")

A.str
B.int
C.tuple
D.list
E.dict

# 答案:
C

97、下面程序的輸出結果是

d = lambda p:p*2 
t = lambda p:p*3

x = 2
x = d(x)
x = t(x)
x = d(x)
print(x)

# 答案
24

98、以下代碼輸出是什么,請給出答案並解釋

def multipliers():
		return [lambda x:x*i for i in range(4)] 
		
print([m(2) for m in multipliers()])

# 答案:
	[6，6，6，6]
	閉包函數延遲綁定問題。
# 請修改 multipliers 的定義來產生期望的結果
def multipliers():
		return [lambda x, i=i:x*i for i in range(4)] 
print([m(2) for m in multipliers()])

99、寫函數

'''
有一個數據結構如下所示，請編寫⼀個函數從該結構數據中返回由指定的字段和對應的值組成的字典。如果指定字段不存在，則跳過該字段。
'''
data:{
    "time":"2016-08-05T13:13:05",
    "some_id":"ID1234",
    "grp1":{"fld1":1, "fld2":2,},
    "xxx2":{"fld3":0, "fld4":0.4,},
		"fld6":11,
		"fld7": 7,
		"fld46":8
}

# fields:由"|"連接的以 fld 開頭的字符串, 如 fld2|fld7|fld29

# 答案一:
def select(data, fields):
    result = {}
    field_lst = fields.split('|')
    for key in data:
        if key in field_lst:
            result[key] = data[key]
        elif type(data[key]) == dict:
            res = select(data[key], fields)
            result.update(res)
    return result


data = {"time": "2016-08-05T13:13:05",
        "some_id": "ID1234",
        "grp1": {"fld1": 1, "fld2": 2},
        "xxx2": {"fld3": 0, "fld5": 0.4},
        "fld6": 11,
        "fld7": 7,
        "fld46": 8}
fields = 'fld2|fld3|fld7|fld19'
print(select(data, fields))

# 答案二:
def select(data,fields,result = {}):
    field_lst = fields.split('|')
    for key in data:
        if key in field_lst:
            result[key] = data[key]
        elif type(data[key]) == dict:
            select(data[key], fields)
    return result
data={"time":"2016-08-05T13:13:05",
    "some_id":"ID1234",
    "grp1":{ "fld1":1,"fld2":2},
    "xxx2":{ "fld3":0,"fld5":0.4},
    "fld6":11,
    "fld7":7,
    "fld46":8}
fields = 'fld2|fld3|fld7|fld19'
select(data,fields)
print(select(data,fields))

100、談談你對閉包的理解？

閉包(closure)是函數式編程的重要的語法結構。閉包也是一種組織代碼的結構，它同樣提高了代碼的可重復使用性。
當一個內嵌函數引用其外部作作用域的變量,我們就會得到一個閉包. 總結一下,創建一個閉包必須滿足以下幾點:

• 必須有一個內嵌函數
• 內嵌函數必須引用外部函數中的變量
• 外部函數的返回值必須是內嵌函數