Python关键字参数额外单词

一个非常简单的Python代码。我希望获得以下资料：

>>> sandwich('wheat')
 'wheat bread sandwich with turkey'
>>> sandwich('white', meat='ham', cheese='American')
 'white bread sandwich with ham and American cheese'
>>> sandwich('white', cheese='American', meat='ham')
'white bread sandwich with ham and American cheese'
>>> sandwich('rye','ham','Swiss')
 'rye bread sandwich with ham and Swiss cheese'
>>> sandwich('white', cheese='provolone')
 'white bread sandwich with turkey and provolone cheese'

这是我的密码。我想在第一句话中忽略任何奶酪。我该怎么做

>>> def sandwich(bread, meat='turkey', cheese=None):
>>>     print bread,"bread sandwich with",meat,"and",cheese,"cheese"


>>> sandwich('wheat')
>>> sandwich('white', meat='ham', cheese='American')
>>> sandwich('white', cheese='American', meat='ham')
>>> sandwich('rye','ham','Swiss')
>>> sandwich('white', cheese='provolone')

---

这是我的密码。我想在第一句话中忽略任何奶酪。我该怎么做？

将默认值从

None

更改为

”

（空字符串）应该可以做到这一点

>>> def sandwich(bread, meat='turkey', cheese=None):
>>>     print bread,"bread sandwich with",meat,"and",cheese,"cheese"


>>> sandwich('wheat')
>>> sandwich('white', meat='ham', cheese='American')
>>> sandwich('white', cheese='American', meat='ham')
>>> sandwich('rye','ham','Swiss')
>>> sandwich('white', cheese='provolone')

编辑： 抱歉，我昨晚没想清楚。将打印行拆分为if检查。如果您的cheese为“”，则打印不带cheese位的行，否则打印您现在的行

很抱歉没有提供代码示例，从我的手机发帖，不应该这样做，我想一个简单的方法是：

def sandwich(bread, meat='turkey', cheese=None):
    print bread,"bread sandwich with",meat,      
    if cheese:
        print "and",cheese,"cheese"

---

你在找这个吗

def sandwich(bread, meat='turkey', cheese=None):
    if cheese:
        print bread,"bread sandwich with",meat,"and",cheese,"cheese"
    else:
        print bread,"bread sandwich with",meat

如果未传递cheese，则从函数定义中获取默认值None。基于此，您可以决定使用奶酪打印句子。

如果没有奶酪，我想删除“and cheese”。它仍然出现“…和奶酪。”