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From: akuchlin at cnri.reston.va.us (Andrew M. Kuchling)
Date: Wed, 28 Apr 1999 11:11:07 -0400 (EDT)
Subject: try vs. has_key()
In-Reply-To: <37247ea3.494305@news.jpl.nasa.gov>
References: <aahzFAM4oJ.M7M@netcom.com>
<yWOT2.6007$8m5.9320@newsr1.twcny.rr.com>
<Pine.SUN.3.95-heb-2.07.990423140345.21577A-100000@sunset.ma.huji.ac.il>
<37247ea3.494305@news.jpl.nasa.gov>
Message-ID: <14119.9202.870049.51888@amarok.cnri.reston.va.us>
X-UID: 94
William H. Duquette writes:
>>>> d = {}
>>>> a = 'Foo'
>>>> d[a] = d.get(a, []).append('Bar')
>>>> d
>{'Foo': None}
>I'd have expected to see {'Foo': 'Bar'}, but that's not what I get.
The .append() method only returns None, not the list you've
just appended to.
>>> L = []
>>> print L.append(2)
None
>>> L
[2]
You'd want something like:
dummy = d[a] = d.get(a, [])
dummy.append('Bar')
--
A.M. Kuchling http://starship.python.net/crew/amk/
When I originally designed Perl 5's OO, I thought about a lot of this stuff,
and chose the explicit object model of Python as being the least confusing. So
far I haven't seen a good reason to change my mind on that.
-- Larry Wall, 27 Feb 1997 on perl5-porters