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multiple constructor __init__
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Chris Rebert  
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 More options Feb 2, 8:24 pm
Newsgroups: comp.lang.python
From: Chris Rebert <c...@rebertia.com>
Date: Thu, 2 Feb 2012 17:24:23 -0800
Local: Thurs, Feb 2 2012 8:24 pm
Subject: Re: multiple constructor __init__
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I believe you can approximate that using a keyword-only argument
without a default value:

# Untested!
# Requires Python 3.x
class QObject(object):
    def __init__(self, param1=some_default, *, parent):
        # …

obj1 = QObject(parent=daddy)
obj2 = QObject(arg1, parent=daddy)

obj3 = QObject(daddy) # ERROR
obj4 = QObject(arg1, daddy) # ERROR
obj5 = QObject() # ERROR

Cheers,
Chris
--
Using names instead of some arbitrary ordering makes much more sense.
http://rebertia.com


 
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Terry Reedy  
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 More options Feb 2, 10:43 pm
Newsgroups: comp.lang.python
From: Terry Reedy <tjre...@udel.edu>
Date: Thu, 02 Feb 2012 22:43:16 -0500
Local: Thurs, Feb 2 2012 10:43 pm
Subject: Re: multiple constructor __init__
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On 2/2/2012 8:09 PM, Emmanuel Mayssat wrote:

> Hello all,

> I would like to instantiate my class as follow

> QObject(<param1>, <parent>)
> QObject(<parent>)

> an example would be
> http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qmenu.html

> How can I do this without have to specify parent=<parent> in the second
> version
> (I always need to supply the parent parameter, but I would like to
> supply it last)

The same way range(stop) versus range(start,stop) works.
But I really recommend against that api.
It makes both doc and code messy.
You need a really good reason to not use the obvious
def __init__(self, parent, param=default):...

--
Terry Jan Reedy


 
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