Python关键字参数附加词

Question

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。我想在我的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。我想在我的第一句话中忽略任何奶酪。我该怎么做？

Answer 1

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

如果不传递奶酪，则从函数定义中获得默认值None。在此基础上，你可以用奶酪决定打印句子。

Answer 2

将默认值从None更改为"" (空字符串)就可以了

编辑:抱歉，深夜没有想清楚。将打印行拆分为if检查。如果你的奶酪是"“打印线没有奶酪位，否则打印的线条，你现在有。

对不起，没有提供代码示例，在我的手机上发帖，我想不应该这样做。

Answer 3

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"