[Python] efficient updating of nested dictionaries

Make a table whose rows are (KEY_X, KEY_Y, KEY_Z, FOO). If the table is
large use MySQL or some other database. For small or medium sized tables
try "http://members.tripod.com/~edcjones/MultiDict.py".

The following is probably too dependent on the data type of the keys,
but it may be suitable in some programs. It's certainly not a general
solution for all cases. Others will have much better ideas, but here
goes anyway ...

You may want to use a non-nested dict with a 'superkey' composed of the
concatenation of the three keys, seperated by some delimiter.
use MY_DICT[KEY_X+'_'+KEY_Y+'_'+KEY_Z]=FOO

Then you could use update().You would just have to do some pre- and
post-processing of the keys. i.e. splitting or joining the 'superkey' by
the delimiter you choose.

Although, that's probably kind of lame - I bet others will have much
better suggestions. I'm interested in how other people do this too.
Rich

So far I have found this on the internet:
def rUpdate(self,targetDict,itemDict):
valtab=[]
for key,val in itemDict.items():
if type(val)==type({}):
newTarget=targetDict.setdefault(key,{})
self.rUpdate(newTarget,val)
else:
targetDict[key]=val

However, this does not seem to handle the fact that each dict has
multiple keys. :( So far the modification I have made to make it work
right have failed. Any ideas?

This is untested code but i think it should work.(fingers crossed)
Btw i doubt this will be fast though.

def rec_update(mydict, newdict):
presentKeysPairs = [(key,value)
for (key, value) in newdict.items()
if mydict.has_key(key)]
newKeysPairs = [(key,value)
for (key, value) in newdict,items()
if not mydict.has_key(key)]
for key, newValue in presentKeysPairs:
currentValue = mydict[key]
if isisntance(newValue, dict):
mydict[key] = rec_update(newValue)
else:
mydict[key] = newValue
mydict.update(dict(newKeysPairs))
return mydict

regards

ps. why can't you simply use tuples to represent the different
dimensions, even if the number of dimensions vary.
is there any particular reason why you are using these nested
dictionaries?

String concatenation is not that lame, but I'd use tuples:
MY_DICT[(KEY_X, KEY_Y, KEY_Z)] = FOO

Tuples save on string operations.

- Josiah

Josiah Carlson <jcarlson at nospam.uci.edu> wrote in
news:bv2e21$j5e$2 at news.service.uci.edu:
I would omit the extra parentheses here, but its a style thing.

MY_DICT[KEY_X, KEY_Y, KEY_Z] = FOO

(Note to original poster: I'd also turn off caps-lock)

What a nice way to simplify this common task. That's great. Thanks for
the advice.
Rich

What a hideous way to complicate this simple medium. That sucks.
Thanks for turning it off in future.

Oh crap. Sorry about the html emails. I've been meaning to turn that
off. Thanks for reminding me.
Rich

Much better! Thanks for being considerate.

omission9 <omission9 at invalid.email.info> wrote in message news:<H%_Qb.2609$925.1917 at nwrddc02.gnilink.net>...
Use a tuple
MY_DICT[(KEY_X,KEY_Y,KEY_Z)]=FOO

unless you have a particular reason to use these nested dicts :)

omission9 <omission9 at invalid.email.info> wrote in message news:<H%_Qb.2609$925.1917 at nwrddc02.gnilink.net>...
Use Tuples

MY_DICT[(KEY_X,KEY_Y,KEY_Z)]=FOO

Unless for some you need to use nested dicts :)

omission9 <omission9 at invalid.email.info> wrote in message news:<H%_Qb.2609$925.1917 at nwrddc02.gnilink.net>...
Use Tuples

MY_DICT[(KEY_X,KEY_Y,KEY_Z)]=FOO

Unless for some you need to use nested dicts :)