try vs. has_key()

[William H. Duquette]

On Wed, 28 Apr 1999 14:58:13 GMT, William.H.Duquette at jpl.nasa.gov
(William H. Duquette) wrote:


>>>> 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.


As someone pointed out, append() returns None, explaining
the result I got.  However, the following code works just fine:

 d = {}
 a = 'foo'

 # Append an entry to d[a], whether it has been initialized or not:
 d[a] = d.get(a, [])
 d[a].append('Bar')


Will

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