Please what is the best way to study python programming well. On Jul 24, 2017 17:00, <tutor-requ...@python.org> wrote:
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Re: basic decorator question (Mats Wichmann) > > > ---------- Forwarded message ---------- > From: Alan Gauld <alan.ga...@yahoo.co.uk> > To: tutor@python.org > Cc: > Bcc: > Date: Mon, 24 Jul 2017 09:27:18 +0100 > Subject: Re: [Tutor] Python3 Help > On 24/07/17 01:58, Alan Gauld via Tutor wrote: > > > $ which python3 > > > >> -bash: $: command not found > > > > The $ is the OS prompt you are not supposed to type it in. > > While on the subject you might also see something like > > # <some command> > > Which can mean one of two things > 1) It's a comment and you should not type it in > 2) It's a root level command and you should su to root > before running it. (# was the default Unix prompt > for super users) > > The latter usage is dying out and usually replaced with > > $ sudo <some command> > > Which means that as an ordinary user ($) you type sudo > before the command. sudo should then prompt for your > user password before carrying out the command. > > But the older # prompt style is still around in some > onlne tutorials. > > -- > Alan G > Author of the Learn to Program web site > http://www.alan-g.me.uk/ > http://www.amazon.com/author/alan_gauld > Follow my photo-blog on Flickr at: > http://www.flickr.com/photos/alangauldphotos > > > > > > ---------- Forwarded message ---------- > From: bruce <badoug...@gmail.com> > To: Python Tutor Mailing List <tutor@python.org> > Cc: > Bcc: > Date: Mon, 24 Jul 2017 10:33:25 -0400 > Subject: [Tutor] basic decorator question > Hi. > > I've seen sites discuss decorators, as functions that "wrap" and > return functions. > > But, I'm sooo confuzed! My real question though, can a decorator have > multiple internal functions? All the examples I've seen so far have a > single internal function. > > And, if a decorator can have multiple internal functions, how would > the calling sequence work? > > But as a start, if you have pointers to any really "basic" step by > step sites/examples I can look at, I'd appreciate it. I suspect I'm > getting flumoxed by something simple. > > thanks > > > > ---------- Forwarded message ---------- > From: Mats Wichmann <m...@wichmann.us> > To: bruce <badoug...@gmail.com>, Python Tutor Mailing List < > tutor@python.org> > Cc: > Bcc: > Date: Mon, 24 Jul 2017 09:49:03 -0600 > Subject: Re: [Tutor] basic decorator question > On 07/24/2017 08:33 AM, bruce wrote: > > Hi. > > > > I've seen sites discuss decorators, as functions that "wrap" and > > return functions. > > > > But, I'm sooo confuzed! My real question though, can a decorator have > > multiple internal functions? All the examples I've seen so far have a > > single internal function. > > > > And, if a decorator can have multiple internal functions, how would > > the calling sequence work? > > > > But as a start, if you have pointers to any really "basic" step by > > step sites/examples I can look at, I'd appreciate it. I suspect I'm > > getting flumoxed by something simple. > > wrap and return are not two distinct things, they're part of the same > process... the general concept is that a decorator changes the result > of a function without modifying the function itself by returning a new > function object which does some other stuff in addition to running the > code of the original function object. > > This is a really simple wrapper: > > def my_decorator(some_function): > def wrapper(): > print("Stuff happening before some_function() is called.") > some_function() > print("Stuff after some_function() is called.") > return wrapper > > If you have an unwrapped function: > > def foo(): > print "This is the unwrapped function" > > You can show this in action like this: > > foo() > bar = my_decorator(foo) > bar() > > function names are just handles to the function object, so the middle > line of those three is passing the original function object referred to > by foo to my_decorator, whose inner function returns a function object > which is runs some code before and after the original function. If the > undecorated fuction does not need to be referred to, the previous often > gets written as: > > foo = my_decorator(foo) > foo() > > Now to add Python's magical decorator syntax: > > @my_decorator > def bar(): > print "This is another unwrapped function" > > bar() > > So all the @my_decorator bit does is provide shorthand for the syntax > > bar = my_decorator(bar) > > Wasn't ultra-clear on your original question; if you wanted the > "happening before" and "happening after" to call out to other functions > instead of doing a print, you can. Is that what you mean by multiple > internal functions? > > Does this clarify at all? > > Do hunt some, there are some really good tutorials on decorators. > > > > _______________________________________________ > Tutor maillist - Tutor@python.org > https://mail.python.org/mailman/listinfo/tutor > > _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
