On 08/01/2010 11:11 PM, Douglas Garstang wrote:
On Sun, Aug 1, 2010 at 10:58 PM, Gary Herron<gher...@islandtraining.com> wrote:
On 08/01/2010 10:09 PM, Douglas Garstang wrote:
Anyone,
I have the two dictionaries below. How can I merge them, such that:
1. The cluster dictionary contains the additional elements from the
default dictionary.
2. Nothing is removed from the cluster dictionary.
The idea here is that the two dictionaries are read from different
files where, if the value isn't found in the cluster dictionary, it's
pulled from the default one, and I can have a new dictionary
reflecting this. The update() method on dictionaries doesn't seem to
work. The resulting dictionary always seems to be the one passed as a
parameter.
default = {
'cluster': {
'platform': {
'elements': {
'data_sources': {
'elements': {
'db_min_pool_size': 10
},
},
},
},
}
}
cluster = {
'cluster': {
'name': 'Customer 1',
'description': 'Production',
'environment': 'production',
'platform': {
'elements': {
'data_source': {
'elements': {
'username': 'username',
'password': 'password'
},
},
},
},
}
}
The resulting dictionary would therefore look like this:
new_dict = {
'cluster': {
'name': 'Customer 1',
'description': 'Production',
'environment': 'production',
'platform': {
'elements': {
'data_source': {
'elements': {
'username': 'username',
'password': 'password',
'db_min_pool_size': 10 # This was added from
the default.
},
},
},
},
}
}
Thanks,
Doug.
Your dictionaries are annoyingly complicated -- making it hard to see what's
going on. Here I've replaced all the distractions of your dictionary
nesting with a simple (string) value. Now when you try to update
default = {'cluster': 'some_value'}
cluster = {'cluster': 'another_value'}
cluster.update(default)
print cluster
{'cluster': 'some_value'}
If you read up on what update is supposed to do, this is correct -- keys in
default are inserted into cluster -- replacing values if they already exist.
I believe update is not what you want for two reasons:
1. It's doubtful that you want a default to replace an existing value, and
that's what update does.
2. I get the distinct impression that you are expecting the update to be
applied recursively down through the hierarchy. Such is not the case.
And I just have to ask: Of what use whatsoever is a dictionary (hierarchy)
that contains *one* single value which needs a sequence of 6 keys to access?
print
default['cluster']['platform']['elements']['data_sources']['elements']['db_min_pool_size']
10
Seems absurd unless there is lots more going on here.
Thanks. Any particular reason you replied off-list?
Huh? Oh hell. My mistake. (This is now back on the list -- where it
should have been to start with.)
Anyway, I'm trying to model a cluster of servers in a yaml file that
gets edited by humans and a tree structure makes it easier to
understand the context of each invidual key. If it was arrange in a
flat fashion, each key would have to be longer in order to make it
unique and provide some context as to what the user was actually
editing.
I actually didn't paste the whole dictionary. I cut it down to make it
easier to explain. When you see the full version, the multiple levels
make more sense. Tried various approaches so far, and none work. I
can't traverse the tree recursively because each time you recurse, you
lose the absolute position of the key your currently at, and then
there's no way to update the values.
Doug.
Ok. Thanks for simplifying things before sending the question out to
the list. You probably wouldn't have gotten a response otherwise.
I'm not sure I believe the reasoning for the inability to recurse. It
seems rather simple to recurse through the structures in tandem, adding
any key:value found in the default to the other if not already present.
Gary Herron
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