json dump throwing TypeError is not JSON serializable on seemingly valid object

Question

Background  I am writing a python program which should manage my music files  It crawls directories and puts the files and their meta data  via mutagen   encoded in JSON  in a file as a simple  database   I have the directory searching fine  but when I try and save the database  or encode to JSON  it throws a  TypeError        is not JSON serializable   the     are some keys and values from a dict  more on that below   The Problem  The program builds a large dictionary object following this format           lt song id gt              artist    lt song artist gt             album    lt song album gt             title    lt song title gt                 Every single song file is indexed via this format  When I try to dump the database to a file  I get this   Traceback  most recent call last     File   lt pyshell 2 gt    line 1  in  lt module gt      sit     File  D  workbench ideas musicmanager v0 spider py   line 116  in sit     json dump js db f True    File  C  Python27 lib json   init   py   line 181  in dump     for chunk in iterable    File  C  Python27 lib json encoder py   line 428  in  iterencode     for chunk in  iterencode dict o   current indent level     File  C  Python27 lib json encoder py   line 402  in  iterencode dict     for chunk in chunks    File  C  Python27 lib json encoder py   line 402  in  iterencode dict     for chunk in chunks    File  C  Python27 lib json encoder py   line 436  in  iterencode     o    default o    File  C  Python27 lib json encoder py   line 178  in default     raise TypeError repr o      is not JSON serializable   TypeError    album    u Rooney s Lost Album     title    u The Kids After Sunset     artist    u Rooney    is not JSON serializable   With the key for that particular song entry being  Rooney Rooney s Lost Album The Kids After Sunset The Kids After Sunset itunes mp3    the format for the id is a little bulky  I might end up hashing that      So I tried to  json dumps   album    u Rooney s Lost Album     title    u The Kids After Sunset     artist    u Rooney       which worked fine  as did  json dumps   Rooney Rooney s Lost Album The Kids After Sunset The Kids After Sunset itunes mp3         And then I tried this   rooney    Rooney Rooney s Lost Album The Kids After Sunset The Kids     After Sunset itunes mp3  json dumps  rooney js db  songsbyid   rooney      Which failed with the type error again   Why does that object fail with json dump  I have plenty of other objects with keys containing pipes     and apostrophes        At the moment  I have no way for anyone else to test this  should I post a pickled version of the database object   Additional Notes   The resulting object below json dumps is fine  so I am wondering if the issue has to do with the size of the database in any way                   rooney js db  songsbyid   rooney           Rooney Rooney s Lost Album The Kids After Sunset The Kids       After Sunset itunes mp3     album    u Rooney s Lost Album           title    u The Kids After Sunset     artist    u Rooney              If I exclude the song by renaming the extension so the script ignores it  another arbitrary song causes the same error  I renamed amp excluded this new song  and ran into ANOTHER new song    I don t know how many there are  I changed my program to crawl the next furthest sub-directory containing the original problem song  and json dump raised a TypeError on a completely different song

User · Answer

In my case  boolean values in my Python dict were the problem  JSON boolean values are in lowercase   true    false   whereas in Python they are in Uppercase   True    False    Couldn t find this solution anywhere online but hope it helps

User · Answer

Because it s not actually a dictionary  it s another mapping type that looks like a dictionary  Use type   to verify  Pass it to dict   to get a real dictionary from it

User · Answer

I wrote a class to normalize the data in my dictionary  The  element  in the NormalizeData class below  needs to be of dict type  And you need to replace  in the   iterate   with either your custom class object or any other object type that you would like to normalize    class NormalizeData       def   init   self  element           self element   element      def execute self           if isinstance self element  dict               self   iterate           else              return      def   iterate self           for key in self element              if isinstance self element key    lt ClassName gt                    self element key    str self element key                node   NormalizeData self element key               node execute

[python] json.dump throwing "TypeError: {...} is not JSON serializable" on seemingly valid object?

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