@func call syntax

[teekaysoh@gmail.com]

Hi,

I am new to Python, here I'd like to have a question: I noticed a
special way to call a function in a program:

@function_name

No argv is passed, even though the function_name asks for one. Any idea
what this @something syntax is trying to achieve. I haven't been able
to find any answer of on the google web and groups.

TIA.

[casevh@comcast.net]

Re: @func call syntax


teekaysoh@gmail .com wrote:[color=blue]
> Hi,
>
> I am new to Python, here I'd like to have a question: I noticed a
> special way to call a function in a program:
>
> @function_name
>
> No argv is passed, even though the function_name asks for one. Any idea
> what this @something syntax is trying to achieve. I haven't been able
> to find any answer of on the google web and groups.
>
> TIA.[/color]

@function_name is called a decorator.

http://www.python.org/dev/peps/pep-0318/

http://docs.python.org/whatsnew/node6.html

casevh

[Schüle Daniel]

Re: @func call syntax

this is decorator, this is how it's may be implented
[color=blue][color=green][color=darkred]
>>> def returns(t):[/color][/color][/color]
.... def dec(f):
.... def wrapped(*args, **kwargs):
.... ret = f(*args, **kwargs)
.... assert type(ret) is t
.... return ret
.... return wrapped
.... return dec
....[color=blue][color=green][color=darkred]
>>>
>>> @returns(int)[/color][/color][/color]
.... def f1():
.... return 1
....[color=blue][color=green][color=darkred]
>>> @returns(float)[/color][/color][/color]
.... def f2():
.... return 2.0
....[color=blue][color=green][color=darkred]
>>> @returns(str)[/color][/color][/color]
.... def f3():
.... return 1
....[color=blue][color=green][color=darkred]
>>> f1()[/color][/color][/color]
1[color=blue][color=green][color=darkred]
>>> f2()[/color][/color][/color]
2.0[color=blue][color=green][color=darkred]
>>> f3()[/color][/color][/color]
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "<stdin>", line 5, in wrapped
AssertionError[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]


I can imagine that stuff like this may be extremely usefull
when testing you program
later one could parse and remove all such assertations
easy and cut them all at once

Regards, Daniel