How to completely traverse a complex dictionary of unknown depth?

You can use a recursive generator for converting your dictionary to flat lists.

def dict_generator(indict, pre=None):    pre = pre[:] if pre else []    if isinstance(indict, dict):        for key, value in indict.items():            if isinstance(value, dict):                for d in dict_generator(value, pre + [key]):                    yield d            elif isinstance(value, list) or isinstance(value, tuple):                for v in value:                    for d in dict_generator(v, pre + [key]):                        yield d            else:                yield pre + [key, value]    else:        yield pre + [indict]

It returns

[u'body', u'kind', u'var'][u'init', u'declarations', u'body', u'type', u'Literal'][u'init', u'declarations', u'body', u'value', 2][u'declarations', u'body', u'type', u'VariableDeclarator'][u'id', u'declarations', u'body', u'type', u'Identifier'][u'id', u'declarations', u'body', u'name', u'i'][u'body', u'type', u'VariableDeclaration'][u'body', u'kind', u'var'][u'init', u'declarations', u'body', u'type', u'Literal'][u'init', u'declarations', u'body', u'value', 4][u'declarations', u'body', u'type', u'VariableDeclarator'][u'id', u'declarations', u'body', u'type', u'Identifier'][u'id', u'declarations', u'body', u'name', u'j'][u'body', u'type', u'VariableDeclaration'][u'body', u'kind', u'var'][u'init', u'declarations', u'body', u'operator', u'*'][u'right', u'init', u'declarations', u'body', u'type', u'Identifier'][u'right', u'init', u'declarations', u'body', u'name', u'j'][u'init', u'declarations', u'body', u'type', u'BinaryExpression'][u'left', u'init', u'declarations', u'body', u'type', u'Identifier'][u'left', u'init', u'declarations', u'body', u'name', u'i'][u'declarations', u'body', u'type', u'VariableDeclarator'][u'id', u'declarations', u'body', u'type', u'Identifier'][u'id', u'declarations', u'body', u'name', u'answer'][u'body', u'type', u'VariableDeclaration'][u'type', u'Program']

UPDATE: Fixed keys list from [key] + pre to pre + [key] as mentioned in comments.

If you only need to walk the dictionary, I'd suggest using a recursive walk function that takes a dictionary and then recursively walks through its elements. Something like this:

def walk(node):    for key, item in node.items():        if item is a collection:            walk(item)        else:            It is a leaf, do your thing

If you also want to search for elements, or query several elements that pass certain criteria, have a look at the jsonpath module.

Instead of writing your own parser, depending on the task, you could extend encoders and decoders from the standard library json module.

I recommend this especially if you need to encode objects belonging to custom classes into the json. If you have to do some operation which could be done also on a string representation of the json, consider also iterating JSONEncoder().iterencode

For both the reference is http://docs.python.org/2/library/json.html#encoders-and-decoders