On 2011-12-08 11:43:12 +0000, Chris Angelico said:
On Thu, Dec 8, 2011 at 10:22 PM, K.-Michael Aye <kmichael....@gmail.com> wrote:
I am still perplexed about decorators though, am happily using Python for
many years without them, but maybe i am missing something?
For example in the above case, if I want the names attached to each other
with a comma, why wouldn't I just create a function doing exactly this? Why
would I first write a single name generator and then decorate it so that I
never can get single names anymore (this is the case, isn't it? Once
decorated, I can not get the original behaviour of the function anymore.
The example given is a toy. It's hardly useful. However, there are a
number of handy uses for decorators; mostly, they consist of giving a
single simple keyword to a complicated set of logic. One example is
the @classmethod and @staticmethod decorators - the code to implement
them could be uglier than nested inline assembly, but you don't have
to care, because you just type "@staticmethod" in front of your def
statement and it does its magic.
Here's a handy trick that I'm sure someone has done in a more
sophisticated way:
def trace(func):
if debugmode:
return lambda *a,**ka:
(print(">"+func.__name__),func(*a,**ka),print("<"+func.__name__))[1]
return func
Then you put @trace in front of all your functions, and if debugmode
is False, nothing will be done - but set it to true, and you get
console output at the entry and exit of each function.
@trace
def test(x):
print("Test! "+x)
return 5
test("asdf")
test
Test! asdf
<test
5
Again, it's helpful because it condenses all the logic (including the
'debugmode' flag) down to a single high level directive: "Trace this
function".
ChrisA
I understand this one, it seems really useful. And maybe i start to
sense some more applicability. Like this, with extra flags that could
be set at run time, I could influence the way a function is executed
without designing the function too complex, but by decorating it, which
at the end could be easier to read than complicated if-then statements
in the function.
Thanks for your example.
Michael
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