On Mon, 13 Oct 2008 14:10:43 +0200, Mathias Frey wrote:
> However incrementing a non-existing key throws an exception. So you
> either have to use a workaround:
>
> >>> try:
> ... counter['B'] += 1
> ... except KeyError:
> ... counter['B'] = 1
>
> Since this looks ugly somebody invented the setdefault method:
>
> >>> counter['B'] = counter.setdefault('B',0) + 1
Nope, for this use case there is the `dict.get()` method:
counter['B'] = counter.get('B', 0) + 1
This assigns only *once* to ``counter['B']`` in every case.
`dict.setdefault()` is for situations where you really want to actually
put the initial value into the dictionary, like with the list example by
the OP.
Ciao,
Marc 'BlackJack' Rintsch
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