通過字典中的鍵循環

因此，我需要在python中定義一些函數，以分別爲每個值打印每個字典鍵。一切都是機場代碼，例如，輸出應該看起來像「從ORD到JFK有直接航班」。而且我需要爲每個機場的每次直飛打印。通過字典中的鍵循環

下面是一個例子輸入

{"ORD" : ["JFK", "LAX", "SFO"], 
"CID" : ["DEN", "ORD"], 
"DEN" : ["CID", "SFO"], 
"JFK" : ["LAX"], 
"LAX" : ["ORD"], 
"SFO" : []}

我的功能是

def printAllDirectFlights(flightGraph): 
    x = len(flightGraph) 
    y = 0 
    while y < x: 
     n = len(flightGraph[y]) 
     z = 0 
     while z < n: 
      print("There is a direct flight from",flightGraph[y],"to",flightGraph[y][z],".")

我想這會工作，但顯然我錯了。我如何通過按鍵循環？我知道，如果我是，例如寫

print(flightGraph["ORD"][0])

然後我會收到JFK作爲輸出，但我怎麼去通過字典的鍵循環？。

來源

2016-04-21 CabooseMSG

您可以通過執行for key in d:（這相當於for key in d.keys()遍歷在字典d鍵下面的示例：

d = {'a': 1, 'b': 2} 
for key in d: 
    print key

會打印：

a 
b

來源

2016-04-21 18:31:33 puzzlepalace

好的，這是有道理的。我修改了代碼，使d = flightGraph。我的第一個循環是鍵入d。但是，當我嘗試運行它時，按照此順序得到。 LAX CID SFO ORD JFK LAX SFO DEN ORD，爲什麼是爲了看似隨意？ – CabooseMSG

使用items()：

for k,v in flightGraph.items(): 
    for c in v: 
     print("There is a direct flight from " + k + " to " + c) 


There is a direct flight from ORD to JFK 
There is a direct flight from ORD to LAX 
There is a direct flight from ORD to SFO 
There is a direct flight from CID to DEN 
There is a direct flight from CID to ORD 
There is a direct flight from JFK to LAX 
There is a direct flight from DEN to CID 
There is a direct flight from DEN to SFO 
There is a direct flight from LAX to ORD

使用sorted(flightGraph.items())如果你想第一個城市按字母順序排列：

for k,v in sorted(flightGraph.items()): 
     for c in v: 
      print("There is a direct flight from " + k + " to " + c) 

There is a direct flight from CID to DEN 
There is a direct flight from CID to ORD 
There is a direct flight from DEN to CID 
There is a direct flight from DEN to SFO 
There is a direct flight from JFK to LAX 
There is a direct flight from LAX to ORD 
There is a direct flight from ORD to JFK 
There is a direct flight from ORD to LAX 
There is a direct flight from ORD to SFO

來源

2016-04-21 18:33:43

謝謝你的幫助！ – CabooseMSG

如果鍵的長度可超過1作爲一個更一般的方式，你可以遍歷所有的鍵與他們相對的產品值，並得到所有的對：

>>> from itertools import product 
>>> for k, v in the_dict.items(): 
...  for i, j in product((k,), v): 
...  print("There is a direct flight from {} to {}".format(i, j)) 
... 
There is a direct flight from JFK to LAX 
There is a direct flight from CID to DEN 
There is a direct flight from CID to ORD 
There is a direct flight from LAX to ORD 
There is a direct flight from DEN to CID 
There is a direct flight from DEN to SFO 
There is a direct flight from ORD to JFK 
There is a direct flight from ORD to LAX 
There is a direct flight from ORD to SFO

注意的是，雖然dict.items不給你一個有序的結果，如果你想獲得的訂單爲您的輸入順序，你最好使用OrderedDict從collection模塊保護你鍵值對。

來源

2016-04-21 18:33:48 Kasramvd

謝謝，我感謝您的幫助！ – CabooseMSG

通過字典中的鍵循環

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