On Thu, 02 Aug 2007 06:32:11 +0000, james_027 wrote:
> hi
>
> for example I have this dictionary
>
> dict = {'name':'james', 'language':'english'}
First of all, this is a bad name because it shadows (overwrites) the
reference to the builtin constructor, `dict`.
> value = 'sex' in dict and dict['sex'] or 'unknown'
>
> is a right pythonic of doing this one? I am trying to get a value from
> the dict, but if the key doesn't exist I will provide one.
If you're using using Python 2.5, you could do this without `and`/`or`
trickery::
>>> d['name'] if 'name' in d else 'unknown'
'james'
>>> d['sex'] if 'sex' in d else 'unknown'
'unknown'
But there are more elegant ways. For example, the `get` method::
>>> d.get('name', 'unknown')
'james'
>>> d.get('sex', 'unknown')
'unknown'
See the `Python Library Reference, 3.8: Mapping types <http://
docs.python.org/lib/typesmapping.html#l2h-294>` for more information on
`dict` methods.
Or you could use the `collections.defaultdict <http://docs.python.org/lib/
defaultdict-objects.html>` type (new in 2.5, too), which I consider most
elegant::
>>> from collections import defaultdict
>>> d2 = defaultdict(lambda:'unknown', d)
>>> d2['name']
'james'
>>> d2['sex']
'unknown'
HTH,
Stargaming
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