OrderedDict KeyError

Question

import collections

d = collections.defaultdict(dict)

d["i"]["a"] = "111"
d["i"]["b"] = "222"

print d

od = collections.OrderedDict()

od["i"]["a"] = "111"
od["i"]["b"] = "222"

print od

Output:

defaultdict(<type 'dict'>, {'i': {'a': '111', 'b': '222'}})
Traceback (most recent call last):
  File "app_main.py", line 51, in run_toplevel
  File "/Users/adam/Desktop/collections.py", line 12, in <module>
    od["i"]["a"] = "111"
KeyError: 'i'

Why the key error with OrderedDict and what I can do about it?

Thanks.

score 2 · Accepted Answer · edited May 23 '17 at 12:15

2

An OrderedDict is not also a defaultdict. You'd have to do something like this:

import collections
od = collections.OrderedDict()
od["i"] = collections.OrderedDict()
od["i"]["a"] = "111"
od["i"]["b"] = "222"
print od

Output:

OrderedDict([('i', OrderedDict([('a', '111'), ('b', '222')]))])

See this answer for a potential ordered defaultdict implementation.

edited May 23 '17 at 12:15

Community

1
1

answered Mar 07 '13 at 23:11

Claudiu

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With this I lose the insertion order which is why I am using OrderedDict – Adam Mar 07 '13 at 23:14
@AdamSilver: then use an `OrderedDict` for the inner one, too. I updated my answer. – Claudiu Mar 07 '13 at 23:15

score 1 · Answer 2 · answered Nov 27 '15 at 07:03

Thats the main advantage of defaultdict especially, it will capture the Keyerror and call the function passed as the argument to defaultdict. But OrderedDict is for different purpose.

If a new dataStrcture combines both functionality would be beneficial. Also, using userDict() it must be possible to implement such a functionality.

You can refer my article on Python Collections

https://techietweak.wordpress.com/2015/11/11/python-collections/

Hope this helps.

OrderedDict KeyError

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