What causes the error pickle UnpicklingError invalid load key

Question

I m trying to storage 5000 data elements on an array  This 5000 elements are storage on an existent file  therefore it s not empty      But I m getting an error and I don t know what is causing it   IN   def array         name    puntos df4       m   open name   rb       v      5000      m seek -5000  io SEEK END      fp   m tell       sz   os path getsize name       while fp  lt  sz          pt   pickle load m          v append pt       m close       return v   OUT   line 23  in array pt   pickle load m   pickle UnpicklingError  invalid load key

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If you transferred these files through disk or other means  it is likely they were not saved properly

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I had a similar error but with different context when I uploaded a   p file to Google Drive  I tried to use it later in a Google Colab session  and got this error      1 with open  quot  tmp train p quot   mode  rb   as training data  ---- gt  2     train   pickle load training data  UnpicklingError  invalid load key    lt     I solved it by compressing the file  upload it and then unzip on the session  It looks like the pickle file is not saved correctly when you upload download it so it gets corrupted

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I am not completely sure what you re trying to achieve by seeking to a specific offset and attempting to load individual values manually  the typical usage of the pickle module is     save data to a file with open  myfile pickle   wb   as fout      pickle dump  1 2 3  fout     read data from a file with open  myfile pickle   as fin      print pickle load fin     output  gt  gt   1  2  3    If you dumped a list  you ll load a list  there s no need to load each item individually   you re saying that you got an error before you were seeking to the -5000 offset  maybe the file you re trying to read is corrupted   If you have access to the original data  I suggest you try saving it to a new file and reading it as in the example

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pickling is recursive  not sequential   Thus  to pickle a list  pickle will start to pickle the containing list  then pickle the first element    diving into the first element and pickling dependencies and sub-elements until the first element is serialized  Then moves on to the next element of the list  and so on  until it finally finishes the list and finishes serializing the enclosing list   In short  it s hard to treat a recursive pickle as sequential  except for some special cases   It s better to use a smarter pattern on your dump  if you want to load in a special way   The most common pickle  it to pickle everything with a single dump to a file -- but then you have to load everything at once with a single load   However  if you open a file handle and do multiple dump calls  e g  one for each element of the list  or a tuple of selected elements   then your load will mirror that    you open the file handle and do multiple load calls until you have all the list elements and can reconstruct the list   It s still not easy to selectively load only certain list elements  however   To do that  you d probably have to store your list elements as a dict  with the index of the element or chunk as the key  using a package like klepto  which can break up a pickled dict into several files transparently  and enables easy loading of specific elements   Saving and loading multiple objects in pickle file

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This may not be relevant to your specific issue  but I had a similar problem when the pickle archive had been created using gzip   For example if a compressed pickle archive is made like this   import gzip  pickle with gzip open  test pklz    wb   as ofp      pickle dump  1 2 3   ofp    Trying to open it throws the errors   with open  test pklz    rb   as ifp       print pickle load ifp   Traceback  most recent call last     File   lt stdin gt    line 2  in  lt module gt   pickle UnpicklingError  invalid load key        But  if the pickle file is opened using gzip all is harmonious  with gzip open  test pklz    rb   as ifp      print pickle load ifp     1  2  3

[python] What causes the error "_pickle.UnpicklingError: invalid load key, ' '."?

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