Parsing an unknown data structure in python

Question

I have a file containing lots of data put in a form similar to this:

Group1 {  
    Entry1 {  
        Title1 [{Data1:Member1, Data2:Member2}]  
        Title2 [{Data3:Member3, Data4:Member4}]  
    }  
    Entry2 {  
        ...  
    }  
}
Group2 {
    DifferentEntry1 {
        DiffTitle1 {
            ...
        }
    }
}

Thing is, I don't know how many layers of parentheses there are, and how the data is structured. I need modify the data, and delete entire 'Entry's depending on conditions involving data members before writing everything to a new file. What's the best way of reading in a file like this? Thanks!

Answer 1

The data structure basically seems to be a dict where they keys are strings and the value is either a string or another dict of the same type, so I'd recommend maybe pulling it into that sort of python structure,

eg:

{'group1': {'Entry2': {}, 'Entry1': {'Title1':{'Data4': 'Member4',
'Data1': 'Member1','Data3': 'Member3', 'Data2': 'Member2'}, 
'Title2': {}}}

At the top level of the file you would create a blank dict, and then for each line you read, you use the identifier as a key, and then when you see a { you create the value for that key as a dict. When you see Key:Value, then instead of creating that key as a dict, you just insert the value normally. When you see a } you have to 'go back up' to the previous dict you were working on and go back to filling that in.

I'd think this whole parser to put the file into a python structure like this could be done in one fairly short recursive function that just called itself to fill in each sub-dict when it saw a { and then returned to its caller upon seeing }

Answer 2

Here is a grammar.

dict_content : NAME ':' NAME [ ',' dict_content ]?
             | NAME '{' [ dict_content ]? '}' [ dict_content ]?
             | NAME '[' [ list_content ]? ']' [ dict_content ]?
             ;

list_content : NAME [ ',' list_content ]?
             | '{' [ dict_content ]? '}' [ ',' list_content ]?
             | '[' [ list_content ]? ']' [ ',' list_content ]?
             ;

Top level is dict_content.

I'm a little unsure about the comma after dicts and lists embedded in a list, as you didn't provide any example of that.