I am following this example Can I do an ordered, default dict in Python?
But when i use this
if mydict['item']`
then i am getting the key error. It should not give me that error.
Shouldn't it suppose to be empty even if key don't exist
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Do you create `mydict` with `default_factory` argument? – gatto Apr 26 '13 at 03:34
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It works for me using that recipe. Can you show a simple reproducible example? – mgilson Apr 26 '13 at 03:38
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no , how should i do that – user2294401 Apr 26 '13 at 03:38
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1@gatto -- Ooo ... Good call. If you create it with no `default_factory` then it implicitly gets set to `None` which would cause the KeyError. – mgilson Apr 26 '13 at 03:39
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Alternatively just use the `dict.get` and `dict.setdefault` methods alongside a normal `OrderedDict` – jamylak Apr 26 '13 at 03:40
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@user2294401 -- It'd just be something like: `mydict = DefaultOrderedDict(func)` where `func` is a function which takes 0 arguments and returns whatever "default" value you want the defaultdict to have. – mgilson Apr 26 '13 at 03:40
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FWIW -- I never realized you could create a `defaultdict` without setting the `default_factory`. Very interesting. – mgilson Apr 26 '13 at 03:42
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I am using like this `d = DefaultOrderedDict(list)` – user2294401 Apr 26 '13 at 03:42
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2Show us the whole code, except for the class. – gatto Apr 26 '13 at 03:48
1 Answers
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To have default values in your dict, you have to set default_factory, which must be a callable.
Example usage:
d = DefaultOrderedDict(lambda: None)
assert d['item'] is None
# as with normal dict, you can init it with another dict
d = {'key': 'value'}
d = DefaultOrderedDict(list, d)
assert d['item'] == []
assert d['key'] == 'value'
gatto
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is there any way that if i already have normal dict and i convert that to DefaultDict. I think i am coverting thata to json and ethen from json coverting back to dict by json.loads() , so think i ahve lost that during conversion – user2294401 Apr 26 '13 at 03:50