Path: csiph.com!usenet.pasdenom.info!news.redatomik.org!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
From: "Ivan Evstegneev" <webmailgroups@gmail.com>
To: "'Terry Reedy'" <tjreedy@udel.edu>, <python-list@python.org>
References: <009d01d06723$38860d50$a99227f0$@gmail.com> <meuvkb$e5t$1@ger.gmane.org>
In-Reply-To: <meuvkb$e5t$1@ger.gmane.org>
Subject: RE: Function Defaults - avoiding unneccerary combinations of arguments at input
Date: Wed, 25 Mar 2015 21:50:40 +0200
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Thread-Index: AQJmhzuVcfXrhgB79AcdClmCd0UxfgEFs1iim/ksjfA=
Content-Language: en-us
Precedence: list
Newsgroups: comp.lang.python
Message-ID: <mailman.158.1427313051.10327.python-list@python.org>
Lines: 88
NNTP-Posting-Host: 2001:888:2000:d::a6
Xref: csiph.com comp.lang.python:87972

Hello again ^_^,

Googled a bit, and found only one, a "ValueError" exception, but still don't
understand how it should be implemented in my case.

Should my code look like this one: 

def  my_fun(history=False, built=False, current=False, topo=None,
full=False, file=None):
	try:
		if currnet and full:
			do something_1
		elif current and file:
			do something_2
		elif history and full and file:
			do something_3
	
	except ValueError:
		print("No valid input! Please try again ...")

	
	...... some code here..............


Or I'm just too optimistic ^_^? 

Thanks in advance,

Ivan.

> -----Original Message-----
> From: Python-list [mailto:python-list-
> bounces+webmailgroups=gmail.com@python.org] On Behalf Of Terry Reedy
> Sent: Wednesday, March 25, 2015 20:43
> To: python-list@python.org
> Subject: Re: Function Defaults - avoiding unneccerary combinations of
> arguments at input
> 
> On 3/25/2015 1:43 PM, Ivan Evstegneev wrote:
> > Hello all ,
> >
> >
> > Just a little question about function's default arguments.
> >
> > Let's say I have this function:
> >
> > def  my_fun(history=False, built=False, current=False, topo=None,
> > full=False, file=None):
> > 	if currnet and full:
> > 		do something_1
> > 	elif current and file:
> > 		do something_2
> > 	elif history and full and file:
> > 		do something_3
> >
> >
> > 	...... some code here..............
> >
> > and so on...
> >
> > I won't cover all the possibilities here (actually I don't use all of
> > them ^_^).
> >
> > The question is about avoiding the response for unnecessary
> combinations?
> >
> > For instance, if user will call function this way:
> >
> >
> >>>> my_fun(current=True, full=True, topo='some str', file="some_file")
> >
> > That will lead to function's misbehavior. As a particular case it will
> > choose "current and full" condition.
> >
> >
> > What is the common accepted way to deal with such unwanted situations?
> 
> Raise a value error for illegal combinations.  There are a few instances
in the
> stdlib where 2 of several options are mutually incompatible.
> 
> 
> --
> Terry Jan Reedy
> 
> --
> https://mail.python.org/mailman/listinfo/python-list