Python关键字输出解释 [英] Python keyword output interpretation

问题描述

我正在阅读Python 2.7教程，并且正在查看以下语句的输出:

I'm going through the Python 2.7 tutorial, and I was looking at the output of the following statement:

def cheeseshop(kind, *arguments, **keywords):
    print "-- Do you have any", kind, "?"
    print "-- I'm sorry, we're all out of", kind
    for arg in arguments:
        print arg
    print "-" * 40
    keys = sorted(keywords.keys())
    for kw in keys:
        print kw, ":", keywords[kw]

因此，如果我这样调用程序:

So, if I call the program as such:

cheeseshop("Cheddar", "No.", "Seriously?",
       Shopkeeper="Michael Palin",
       Client="John Cleese")

它输出:

Do you have any Cheddar?
I'm sorry, we're all out of Cheddar
No.
Seriously?
--------------------------------------
Client: John Cleese
Shopkeeper: Michael Palin

这是正确的.

如果将打印语句更改为print keywords，则会得到以下表示形式:

If I change that print statement to print keywords, I get the following representation:

{'Shopkeeper': 'Ryan Lambert', 'Client': 'John Cleese'}

我对打印keywords[kw]只是返回名称而keywords没有返回名称感到困惑.

I'm a bit confused on how printing keywords[kw] just comes back with a name, and keywords does not.

推荐答案

在Python中，您可以通过在功能参数列表的前面放置**来传递可选的关键字参数.

In Python, you can pass optional keyword parameters by putting a ** in front of the function parameter's list.

因此，keywords变量实际上是字典类型.因此，如果您这样做:

So the keywords variable is actually a dictionary type. Thus, if you do:

print keywords

您回来了(重新格式化以使映射更加明显)

you get back (reformatted to make the mapping more obvious)

{
    'Shopkeeper': 'Ryan Lambert', 
    'Client': 'John Cleese'
}

这是一本字典.如果您这样做:

which is a dictionary. And if you do:

print keywords[kw]

您将获得与键kw关联的字典的值.因此，如果kw是'Shopkeeper'，则keywords[kw]变成'Ryan Lambert'，如果kw是'Client'，则keywords[kw]变成'John Cleese'

you get back the value of the dictionary associated with the key kw. So if kw was 'Shopkeeper', then keywords[kw] becomes 'Ryan Lambert', and if kw was 'Client', then keywords[kw] becomes 'John Cleese'

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