Python：如何修改嵌套字典中的值并返回整个字典

Question

Imagine that I have got a file named 'test_dict.txt' containing the following dictionary-like text:

{
    "subdic1" : {
        "a_string" : "something1",
        "a_integer" : 16,
        "a_list" : [
            "str_1",
            "str_2"
        ]
    },
    "subdic2" : {
        "a_string" : "something2",
        "a_integer" : 32,
        "a_list" : [
            "str_3",
            "str_4"
        ]
    }
}

As you can see that there are nested dictionaries. What I want to do is to convert all deepest values ("something1", 16, ["str_1", "str_2"], etc) to unicode type objects, for some comparison purposes. Here is my attempt:

import json
from copy import deepcopy

def to_unicode(d):
    dc = deepcopy(d)
    for k,v in dc.iteritems():
        if isinstance(v, dict):
            to_unicode(v)
        else:
            dc[k] = unicode(v)
    return dc

dict_fname = 'test_dict.txt'
with open(dict_fname) as dict_fd:
    dic = json.load(dict_fd)
print dic
print to_unicode(dic)

I used recursion in my function 'to_unicode' in order to traverse to the deepest values. The first 'print' gives the result of 'json.load' operation like the following:

{u'subdic1': {u'a_list': [u'str_1', u'str_2'], u'a_integer': 16, u'a_string': u'something1'}, u'subdic2': {u'a_list': [u'str_3', u'str_4'], u'a_integer': 32, u'a_string': u'something2'}}

So what I should really convert to unicode type is the two integers 16 and 32. But I still want the function to convert each value inside each level of dictionary for the purpose of simplicity. The two numbers are supposed to be converted to u'16' and u'32', so the dictionary object returned by the function should be printed like this:

{u'subdic1': {u'a_list': [u'str_1', u'str_2'], u'a_integer': u'16', u'a_string': u'something1'}, u'subdic2': {u'a_list': [u'str_3', u'str_4'], u'a_integer': u'32', u'a_string': u'something2'}}

But in fact my second 'print' gives the exactly same result as the first one. I guess the issue occurs either in deepcopy or in the way of return of the function, or even both. I really want the whole dictionary to be returned back after the conversion, rather than yielding one item a time. Could somebody help correcting my code please?

Answer 1

As @jonrsharpe mentioned you just need to assign things back to the master or original copy. Here's some spaghetti that iterates on the code you've provided :

def to_unicode(d, target_dict={}):
    for k,v in d.iteritems(): 
        if isinstance(v, dict): 
            target_dict = to_unicode(v, target_dict)
        else: 
            target_dict[k] = unicode(v)
    return target_dict