在 2012年2月17日星期五UTC+8下午5时55分11秒，Nobody写道：
> On Fri, 17 Feb 2012 16:53:00 +0900, Zheng Li wrote:
>
> > def method1(a = None):
> > print a
> >
> > i can call it by
> > method1(*(), **{'a' : 1})
> >
> > I am just curious why it works and how it works?
> > and what do *() and **{'a' : 1} mean?
>
> In a function call, an argument consisting of * followed by an expression
> of tuple type inserts the tuple's elements as individual positional
> arguments. An argument consisting of ** followed by an expression of
> dictionary type inserts the dictionary's elements as individual keyword
> arguments.
>
> So if you have:
>
> a = (1,2,3)
> b = {'a': 1, 'b': 2, 'c': 3}
>
> then:
>
> func(*a, **b)
>
> is equivalent to:
>
> func(1, 2, 3, a = 1, b = 2, c = 3)
>
> > when I type *() in python shell, error below happens
> >
> > File "<stdin>", line 1
> > *()
> > ^
> > SyntaxError: invalid syntax
>
> The syntax described above is only valid within function calls.
>
> There is a similar syntax for function declarations which does the reverse:
>
> > def func(*a, **b):
> print a
> print b
>
> > func(1, 2, 3, a = 1, b = 2, c = 3)
> (1, 2, 3)
> {'a': 1, 'c': 3, 'b': 2}
In the functional programming view, 2 to 5
object parameters are enough to invoke a function.
But the tuple and dictionary packing and unpacking
are not free in the run time.
Enhancement to operations of basic types in Python can speed up everything.
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