Dictionary of Dictionaries

[bg_ie]

Hi,

I have the following -

messagesReceived = dict.fromkeys(("one","two"), {})

messagesReceived['one']['123'] = 11111
messagesReceived['two']['121'] = 22222
messagesReceived['two']['124'] = 43333

This gives:

{'two': {'121': 22222, '123': 11111, '124': 43333}, 'one': {'121':
22222, '123': 11111, '124': 43333}}

but I expected -

{'one': {'121': 22222, }, 'two': {'123': 11111, '124': 43333}}

What am I doing wrong?

Thanks,

Barry.

 

[Amit Khemka]

Hi,

I have the following -

messagesReceived = dict.fromkeys(("one","two"), {})

This will create a dictionary "messagesReceived", with all the keys
referring to *same instance* of the (empty) dictionary.
( try: messagesReceived = dict( [(k,{}) for k in ('one', 'two') ] ) )

messagesReceived['one']['123'] = 11111
messagesReceived['two']['121'] = 22222
messagesReceived['two']['124'] = 43333

This gives:

{'two': {'121': 22222, '123': 11111, '124': 43333}, 'one': {'121':
22222, '123': 11111, '124': 43333}}

And hence the results !


HTH,

--

 

[Marc 'BlackJack' Rintsch]

What am I doing wrong?

`dict.fromkeys()` stores the given object for all keys, so you end up with
the *same* dictionary for 'one' and 'two'.

In [18]: a = dict.fromkeys(("one","two"), {})

In [19]: a
Out[19]: {'two': {}, 'one': {}}

In [20]: a['one']['x'] = 42

In [21]: a
Out[21]: {'two': {'x': 42}, 'one': {'x': 42}}

In [22]: a['one'] is a['two']
Out[22]: True

Ciao,
Marc 'BlackJack' Rintsch

 

[bg_ie]

Hi,

I have the following -

messagesReceived = dict.fromkeys(("one","two"), {})

This will create a dictionary "messagesReceived", with all the keys
referring to *same instance* of the (empty) dictionary.
( try: messagesReceived = dict( [(k,{}) for k in ('one', 'two') ] ) )

messagesReceived['one']['123'] = 11111
messagesReceived['two']['121'] = 22222
messagesReceived['two']['124'] = 43333

This gives:

{'two': {'121': 22222, '123': 11111, '124': 43333}, 'one': {'121':
22222, '123': 11111, '124': 43333}}

And hence the results !

HTH,

--
----
Amit Khemka -- onyomo.com
Home Page:www.cse.iitd.ernet.in/~csd00377
Endless the world's turn, endless the sun's Spinning, Endless the quest;
I turn again, back to my own beginning, And here, find rest.

Thanks for your help!

 

[Bart Ogryczak]

messagesReceived = dict.fromkeys(("one","two"), {})

This creates two references to just *one* instance of empty
dictionary.
I'd do it like:
messagesReceived = dict([(key, {}) for key in ("one","two")])

 

[Duncan Booth]

messagesReceived = dict.fromkeys(("one","two"), {})

This creates two references to just *one* instance of empty
dictionary.
I'd do it like:
messagesReceived = dict([(key, {}) for key in ("one","two")])

Alternatively use a defaultdict (Python 2.5) and you don't need to know the
keys in advance:

from collections import defaultdict
messagesReceived = defaultdict(dict)
messagesReceived['one']['123'] = 11111
messagesReceived['two']['121'] = 22222
messagesReceived['two']['124'] = 43333
messagesReceived

defaultdict(<type 'dict'>, {'two': {'121': 22222, '124': 43333}, 'one':
{'123': 11111}})