On Fri, Sep 30, 2016 at 6:55 AM, Steven D'Aprano <st...@pearwood.info> wrote:
> On Thu, Sep 29, 2016 at 09:43:57PM -0500, boB Stepp wrote:
>> But why does Python require
>> separating the function object from its parameters when it is being
>> passed as an argument to another function?
>
> If you pass the function arguments to the function *first*, then it gets
> evaluated before the second function gets to see it. Let's investigate:
>
> def g(*args):
> print("Calling function g with arguments {}".format(args))
> return 999
>
> def f(func, *args):
> print("f received first argument: {}".format(func))
> print("f received additional arguments: {}".format(args))
> return func(*args)
>
>
> Let's try it the right way:
>
> py> f(g, 1, 2, 3)
> f received first argument: <function g at 0xb7ac965c>
> f received additional arguments: (1, 2, 3)
> Calling function g with arguments (1, 2, 3)
> 999
>
>
>
> And the wrong way:
>
> py> f(g(1, 2, 3))
> Calling function g with arguments (1, 2, 3)
> f received first argument: 999
> f received additional arguments: ()
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "<stdin>", line 4, in f
> TypeError: 'int' object is not callable
>
>
>
> Does this help?
Yes. Thanks, Steve! Very helpful examples.
--
boB
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