相同的函數在Python中以相反順序給出不同的結果。爲什麼？

Question

我使用這個代碼：

def copy_part_of_space(row,column,lenght): 
    #Copy String to Presentation Space (15) 
    #Prerequisite Connect Presentation Space 
    #Prerequisite function: connect_pcomm(presentation_space)  
    function_number = c_int(8) 
    data_string = create_string_buffer(lenght*2*2) #number of unicode char *2*2 
    lenght = c_int(lenght) 
    ps_position = c_int(((row - 1) * 80)+ column) 
    foo = hllapi(byref(function_number), data_string, byref(lenght), byref(ps_position)) 
    data_string.value 
    return {{ 
     0 : 'The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.', 
     1 : 'Your program is not connected to a host session.', 
     4 : 'The host presentation space contents were copied. The connected host  presentation space was waiting for host response.', 
     5 : 'The host presentation space was copied. The keyboard was locked.', 
     9 : 'A system error was encountered.', 
     'x' : 'Undocumented error found. Run in circles.', 
     }.get(foo, 'x'),data_string.value} 

的想法是複製從終端的一些信息;這些函數需要返回狀態信息（使用字典和0,1,4,5,9，x參數）和複製的信息 - 使用data_string.value

要運行一些測試，我使用的代碼使用上面的功能：

for a in range(15,22): 
    print copy_part_of_space(a,7,8) 

這是結果：

set(['The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.', '36343581']) 
    set(['36343663', 'The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.']) 
    set(['The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.', '36343708']) 
    set(['36344673', 'The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.']) 
    set(['36344740', 'The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.']) 
    set(['The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.', '36344758']) 
    set(['36344869', 'The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.']) 

正如你所看到的，有時我得到了從主機應用程序複製之前的狀態信息 - 像第一行。

但有時我會得到狀態信息之前複製的信息，如第二行。

我不熟悉使用dict返回信息，所以我想這可能是一個問題，特別是當與事實我想返回兩個變量混合。

任何人都可以解釋爲什麼會發生這種情況？

我知道我可以簡單地使用dict並在返回之前將返回信息保存到變量中，但我真的認爲這是一個更優雅的解決方案 - 我錯了嗎？

Answer 1

set s是無序的（或更好的，它們的順序是任意的）。除了使用有序的數據類型外，你無能爲力。

例如通過去除set構造{...}：

return { 
    0 : 'The host presentation space contents were copied to the application program. The target presentation space was active, and the keyboard was unlocked.', 
    1 : 'Your program is not connected to a host session.', 
    4 : 'The host presentation space contents were copied. The connected host  presentation space was waiting for host response.', 
    5 : 'The host presentation space was copied. The keyboard was locked.', 
    9 : 'A system error was encountered.', 
    'x' : 'Undocumented error found. Run in circles.', 
    }.get(foo, 'x'), data_string.value 

現在，這個代碼將返回tuple代替（第一個元素是從「錯誤消息辭典」，無論是包含在所述第二個查找結果data_string.value）。

Answer 2

您正在特別返回一個set，它被定義爲無序數據類型。也就是說，一個集合中的元素可以以任何順序返回。套件針對會員資格測試進行了優化（if x in set:）。集合就像字典的鍵：它們可以以任何順序迭代。

我懷疑有更好的數據類型，你會是一個元組：return (a, b)

然後將結果總是以相同的順序。

注意，在文字符號的差異：

• 字典有冒號配對項目：{'a': 'b', 'c': 'd')。
• 集合沒有冒號，而僅僅是任意定製項：{'a', 'b', 'c', 'd'}
• 元組使用圓括號：('a', 'b', 'c', 'd')
• 列表使用方括號，並且是可變的：['a', 'b', 'c', 'd']