[Tutor] creating a nested dictionary

[Garry Willgoose]

Is there any easy way to create a nested dictionary. I want to be  
able to allocate like

pdb[dataset][modulename][parametername]['value']=value

where dataset, modulename, parametername are variables that are  
determined within loops nested 3 deep, and value comes from a  
database call. Prior to the nested loops I do not know what the  
values of dataset, modulename, parametername will range over, but I  
do know pdb needs to be nested 3 deep. What I'd like to do is  
something like this

pdb={}
for dataset in dataset_list:
	modulename_list=getmodules(dataset)
	for modulename in modulename_list:
		parametername_list=getparameters(dataset,modulename)
		for parametername in parametername_list:
			value=getvalue(dataset, modulename, parametername)
			pdb[dataset][modulename][parametername]['value']=value
			
What I'm currently doing is

pdb={}
for dataset in dataset_list:
	modulename_list=getmodules(dataset)
	moduledict={}
	for modulename in modulename_list:
		parametername_list=getparameters(dataset,modulename)
		valuedict={}
		for parametername in parametername_list:
			value=getvalue(dataset, modulename, parametername)
			valuedict['value']=value
#  valuedict needs to be a dictionary because there is other stuff
			valuedict['otherstuff]=otherstuff
...
			parameterdict[parametername]=valuedict.copy()
		moduledict[modeulename]=copy.deepcopy(parameterdict)
	pdb[dataset]=copy.deepcopy(moduledict)


Now I know the 2nd is not that much more complex but this is a pretty  
common construct in what I'm doing so I'm just wondering if there is   
a clear and simple shortcut ;-)


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Prof Garry Willgoose,
Australian Professorial Fellow in Environmental Engineering,
Director, Centre for Climate Impact Management (C2IM),
School of Engineering, The University of Newcastle,
Callaghan, 2308
Australia.

Centre webpage: www.c2im.org.au

Phone: (International) +61 2 4921 6050 (Tues-Fri AM); +61 2 6545 9574  
(Fri PM-Mon)
FAX: (International) +61 2 4921 6991 (Uni); +61 2 6545 9574 (personal  
and Telluric)
Env. Engg. Secretary: (International) +61 2 4921 6042

email:  garry.willgoose at newcastle.edu.au;  
g.willgoose at telluricresearch.com
email-for-life: garry.willgoose at alum.mit.edu
personal webpage: www.telluricresearch.com/garry
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"Do not go where the path may lead, go instead where there is no path  
and leave a trail"
                           Ralph Waldo Emerson
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