Trying to convert dictionary object with keys of type bytes to json using json.dumps(). Format of dictionary object is not known beforehand. Have found solution for arrays or dictionaries with byte values when using json.dumps (Convert bytes embedded in list (or dict) to str for use with json.dumps) but have not found one for byte keys.
import json class BytesDump(json.JSONEncoder): def default(self, obj): if isinstance(obj, bytes): return obj.decode() return json.JSONEncoder.default(self, obj) foo = {'name': b'bob', 'age': 33, 'attributes': {'hair': b'brown', 'arms': 2}} bar = {b'name': b'bob', b'age': 33, b'attributes': {b'hair': b'brown', b'arms': 2}} print(json.dumps(foo, cls=BytesDump)) # this works print(json.dumps(bar, cls=BytesDump)) # this doesn't work
Output from above
{"name": "bob", "age": 33, "attributes": {"hair": "brown", "arms": 2}} Traceback (most recent call last): File "./test.py", line 15, in <module> print(json.dumps(bar, cls=BytesDump)) File "/usr/local/lib/python3.6/json/__init__.py", line 238, in dumps **kw).encode(obj) File "/usr/local/lib/python3.6/json/encoder.py", line 199, in encode chunks = self.iterencode(o, _one_shot=True) File "/usr/local/lib/python3.6/json/encoder.py", line 257, in iterencode return _iterencode(o, 0) TypeError: keys must be a string
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Answer
you could pre-process the dictionary to convert the keys as strings recursively if they’re bytes
import json # your dump code for values, unmodified class BytesDump(json.JSONEncoder): def default(self, obj): if isinstance(obj, bytes): return obj.decode() return json.JSONEncoder.default(self, obj) # recursive key as string conversion for byte keys def keys_string(d): rval = {} if not isinstance(d, dict): if isinstance(d,(tuple,list,set)): v = [keys_string(x) for x in d] return v else: return d for k,v in d.items(): if isinstance(k,bytes): k = k.decode() if isinstance(v,dict): v = keys_string(v) elif isinstance(v,(tuple,list,set)): v = [keys_string(x) for x in v] rval[k] = v return rval print(json.dumps(keys_string(bar), cls=BytesDump))
with:
bar = {b'name': b'bob', b'age': 33, b'attributes': {b'hair': b'brown', b'arms': 2}, b'other': [{b'hair': b'brown', b'arms': 2}]}
prints:
{"attributes": {"hair": "brown", "arms": 2}, "age": 33, "name": "bob", "other": [{"hair": "brown", "arms": 2}]}