我在這個程序中跟蹤派系聯盟的地方在哪裏？

Question

我有一個程序模擬王國和其他羣體（在我的代碼中稱爲「派系」）。

class Faction: 
    def __init__(self, name, allies=[]): 
     self.name = name 
     self.allies = allies 

    def is_ally_of(self, other_faction): 
     if self in other_faction.allies: 
      return True 
     else: 
      return False 

    def become_ally(self, other_faction, both_ally=True): 
     """ If both_ally is false, this does *not* also 
      add self to other_faction's ally list """ 
     if self.is_ally_of(other_faction): 
      print("They're already allies!") 
     else: 
      self.allies.append(other_faction) 
      if both_ally == True: 
       other_faction.become_ally(self, False) 

RezlaGovt = Faction("Kingdom of Rezla") 
AzosGovt = Faction("Azos Ascendancy") 

我希望能夠become_ally（）方法調用一個派別派別添加到盟友名單，像這樣：

RezlaGovt.become_ally(AzosGovt) # Now AzosGovt should be in RezlaGovt.allies, 
           # and RezlaGovt in AzosGovt.allies 

什麼實際發生的是這樣的：

RezlaGovt.become_ally(AzosGovt) 
# prints "They're already allies!" 
# now AzosGovt is in the allies list of both AzosGovt and RezlaGovt, 
# but RezlaGovt isn't in any allies list at all. 

每當我嘗試調用become_ally（）時，代碼應該檢查以確保它們不是盟友。這是不工作的部分。每次我打電話給become_ally（）時，它會打印出「他們已經是盟友！」，無論他們是否真的是。

我也試過使用if self in other_faction.allies:，但是那個問題相同。

我強烈懷疑問題在於我使用了self，但我不知道Google會向Google瞭解哪些條款以獲取更多信息。

Answer 1

You can't use mutable arguments as the default argument to a function.

def __init__(self, name, allies=[]): 

當使用默認情況下，它是相同list每一次，所以它們具有相同的allies;變異的人會改變另一個，因爲他們實際上是同一件事。

更改爲：

def __init__(self, name, allies=None): 
    if allies is None: 
     allies = [] 

另外，無條件地複製allies參數（這樣你就不用擔心對它的引用倖存外班和類下得到的突變）：

def __init__(self, name, allies=[]): 
    self.allies = list(allies) # Which also guarantees a tuple argument becomes list 
           # and non-iterable args are rejected 

Answer 2

更改此功能。

def is_ally_of(self, other_faction): 
     if other_faction in self.allies: 
      return True 
     else: 
      return False 

檢查自己的數據並不是傳入的對象的。

而且

def __init__(self, name, allies=[]): 

是等待發生的錯誤。您的allies列表將成爲所有實例之間共享的靜態列表。而是使用

def __init__(self, name, allies=None): 
     self.name = name 
     self.allies = allies or []