Le Tue, 24 Feb 2009 14:03:09 -0500,
nathan virgil <sdragon1...@gmail.com> s'exprima ainsi:
> I'm experimenting with OOP using the Critter Caretaker script from Python
> Programming for the Absolute Beginner as my basis. I've noticed that a
> dictionary/function combo is a great way to handle menus, and so I've
> adapted the menu to read as:
>
>
> selection = raw_input("Choice: ")
> choices = {"0":quit, "1":crit.talk, "2":crit.eat, "3":crit.play}
> choice = choices[selection]
> choice()
This is (to my taste) very good programming practice. The only detail is that
in this precise case, as keys are ordinals starting at 0, you can use a simple
list instead ;-) and
choice = choices[int(selection)]
> so that I can call methods from a dictionary, instead of having an
> excruciatingly long if structure. Unfortunately, the problem I'm running
> into with this is that I can't pass any perimeters through the dictionary. I
> can't figure out how, for example, I could have an option that calls
> crit.eat(2) and another that calls crit.eat(4). The only thing I can think
> of is going back to the if structure, but my instinct tells me that this is
> a Bad Idea. What can I do?
There is a syntactic trick for this, commonly called *args. You can call a
function and pass it a variable holding a 'pack' of arguments prefixed with '*'
so that the args will be automagically unpacked into the call message. Below an
example:
def sum(a,b):
return a+b
arg_list = (1,2)
func_calls = {1:sum(*arg_list)}
print func_calls[1]
==> 3
Like if I had written sum(1,2) -- except that the arg_list can now be unknown
at design time!
Conversely, when you want a function to accept an arbitrary number of args, you
can write its def using the * trick:
def sum(*values):
s = 0
for v in values : s+= v
return s
print sum(1), sum(1,2), sum(1,2,3)
==> 1, 3, 6
There is a similar trick for named arguments using **
denis
------
la vita e estrany
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