Python for循環在第一次迭代後停止

Question

我在調試下面的函數get_secondary_connections時遇到問題。出於某種原因，我的for friend in network[user][‘connections’]循環始終停在列表中的第一個值上，而不是遍歷整個列表。我不明白爲什麼會這樣。有人能給我一些指導嗎？非常感謝！

這裏是我的網絡：

network = { 

'Freda': {'connections': ['Olive', 'John', 'Debra'], 'favorite games': ['Starfleet Commander', 'Ninja Hamsters', 'Seahorse Adventures']}, 

'Ollie': {'connections': ['Mercedes', 'Freda', 'Bryant'], 'favorite games': ['Call of Arms', 'Dwarves and Swords', 'The Movie: The Game']}, 

'Debra': {'connections': ['Walter', 'Levi', 'Jennie', 'Robin'], 'favorite games': ['Seven Schemers', 'Pirates in Java Island', 'Dwarves and Swords']}, 

'Olive': {'connections': ['John', 'Ollie'], 'favorite games': ['The Legend of Corgi', 'Starfleet Commander']}, 

'Levi': {'connections': ['Ollie', 'John', 'Walter'], 'favorite games': ['The Legend of Corgi', 'Seven Schemers', 'City Comptroller: The Fiscal Dilemma']}, 

'Jennie': {'connections': ['Levi', 'John', 'Freda', 'Robin'], 'favorite games': ['Super Mushroom Man', 'Dinosaur Diner', 'Call of Arms']}, 

'Mercedes': {'connections': ['Walter', 'Robin', 'Bryant'], 'favorite games': ['The Legend of Corgi', 'Pirates in Java Island', 'Seahorse Adventures']}, 

'John': {'connections': ['Bryant', 'Debra', 'Walter'], 'favorite games': ['The Movie: The Game', 'The Legend of Corgi', 'Dinosaur Diner']}, 

'Robin': {'connections': ['Ollie'], 'favorite games': ['Call of Arms', 'Dwarves and Swords']}, 

'Bryant': {'connections': ['Olive', 'Ollie', 'Freda', 'Mercedes'], 'favorite games': ['City Comptroller: The Fiscal Dilemma', 'Super Mushroom Man']}, 

'Walter': {'connections': ['John', 'Levi', 'Bryant'], 'favorite games': ['Seahorse Adventures', 'Ninja Hamsters', 'Super Mushroom Man']} } 

這裏是我的代碼：

def get_secondary_connections(network, user): 
    if user not in network: 
     return None 
    sec_connections = [] 
    for friend in network[user]['connections']: 
     for connection in network[friend]['connections']: 
      if connection not in sec_connections: 
       sec_connections.append(connection) 
    return sec_connections 

當我運行get_secondary_connections（網絡，「奔馳」），我得到下面的輸出：

[‘John’, ‘Levi’, ‘Bryant’] 

其中，如果您在我的網絡中查看過，那只是Walter的連接列表。我應該得到奔馳的次級連接的完整列表，那就是：

[‘John’, ‘Levi’, ‘Bryant’, ‘Ollie’, ‘Olive’, Freda’, ‘Mercedes’] 

有人能幫我嗎？

Answer 1

我複製粘貼你的代碼並運行程序，並得到了輸出：

['John', 'Levi', 'Bryant', 'Ollie', 'Olive', 'Freda', 'Mercedes'] 

該輸出你想要的，對不對？你的代碼沒有問題。如果你願意，這是代碼的外觀：

network = { 
'Freda': {'connections': ['Olive', 'John', 'Debra'], 'favorite games': ['Starfleet Commander', 'Ninja Hamsters', 'Seahorse Adventures']}, 

'Ollie': {'connections': ['Mercedes', 'Freda', 'Bryant'], 'favorite games': ['Call of Arms', 'Dwarves and Swords', 'The Movie: The Game']}, 

'Debra': {'connections': ['Walter', 'Levi', 'Jennie', 'Robin'], 'favorite games': ['Seven Schemers', 'Pirates in Java Island', 'Dwarves and Swords']}, 

'Olive': {'connections': ['John', 'Ollie'], 'favorite games': ['The Legend of Corgi', 'Starfleet Commander']}, 

'Levi': {'connections': ['Ollie', 'John', 'Walter'], 'favorite games': ['The Legend of Corgi', 'Seven Schemers', 'City Comptroller: The Fiscal Dilemma']}, 

'Jennie': {'connections': ['Levi', 'John', 'Freda', 'Robin'], 'favorite games': ['Super Mushroom Man', 'Dinosaur Diner', 'Call of Arms']}, 

'Mercedes': {'connections': ['Walter', 'Robin', 'Bryant'], 'favorite games': ['The Legend of Corgi', 'Pirates in Java Island', 'Seahorse Adventures']}, 

'John': {'connections': ['Bryant', 'Debra', 'Walter'], 'favorite games': ['The Movie: The Game', 'The Legend of Corgi', 'Dinosaur Diner']}, 

'Robin': {'connections': ['Ollie'], 'favorite games': ['Call of Arms', 'Dwarves and Swords']}, 

'Bryant': {'connections': ['Olive', 'Ollie', 'Freda', 'Mercedes'], 'favorite games': ['City Comptroller: The Fiscal Dilemma', 'Super Mushroom Man']}, 

'Walter': {'connections': ['John', 'Levi', 'Bryant'], 'favorite games': ['Seahorse Adventures', 'Ninja Hamsters', 'Super Mushroom Man']} 
} 

def get_secondary_connections(network, user): 
    if user not in network: 
     return None 
    sec_connections = [] 
    for friend in network[user]['connections']: 
     for connection in network[friend]['connections']: 
      if connection not in sec_connections: 
       sec_connections.append(connection) 
    return sec_connections 

print get_secondary_connections(network, "Mercedes")