访问列表/字典的任意嵌套结构中的元素

Question

I have nested structure of python lists and dictionaries.

tree = { 'blah': [ "booz", {'foobar': [ { 'somekey': 'someval' } ] } ] }

I also have several recursive functions that allow me to traverse tree hierarchy from top to bottom and return keys and values that I need. eg.:

def get_objectcontent(obj, objid):

    result = None

    if isinstance(obj, dict):
        for key, val in obj.items():
            if key == objid:
                result = val
            elif isinstance(val, list) or isinstance(val, dict):
                retval = get_objectcontent(val, objid)
                if retval is not None:
                    result = retval
    elif isinstance(obj, list):
        for elem in obj:
            if isinstance(elem, list) or isinstance(elem, dict):
                retval = get_objectcontent(elem, objid)
                if retval is not None:
                    result = retval

    return result

Unfortunately, I want to modify the data in tree too and that is the problem. Only possible solution that I can see is to construct the 'path' to element dynamically while walking down through the tree and construct something like:

tree['blah'][1]['foobar'][0]['somekey']) = 'newval'

I didn't found any way how could I point to my key in Python (when I know where in structure it is).

Is there some other, more intelligent way to solve this in Python 3?

Answer 1

You're ultimately looking for objid as a key in a dict , so you can change:

result = val

to:

result = obj

Then the caller can do:

result[objid] = new_val

You might also consider replacing the assignments to result with return statements, assuming you don't mind getting the first instance rather than the last.