ValueError Wrong number of items passed - Meaning and suggestions

Question

I am receiving the error  ValueError  Wrong number of items passed 3  placement implies 1  and I am struggling to figure out where  and how I may begin addressing the problem   I don t really understand the meaning of the error  which is making it difficult for me to troubleshoot   I have also included the block of code that is triggering the error in my Jupyter Notebook   The data is tough to attach  so I am not looking for anyone to try and re-create this error for me   I am just looking for some feedback on how I could address this error   KeyError                                  Traceback  most recent call last  C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas indexes base py in get loc self  key  method  tolerance     1944             try  - gt  1945                 return self  engine get loc key     1946             except KeyError   pandas index pyx in pandas index IndexEngine get loc  pandas index c 4154     pandas index pyx in pandas index IndexEngine get loc  pandas index c 4018     pandas hashtable pyx in pandas hashtable PyObjectHashTable get item  pandas hashtable c 12368     pandas hashtable pyx in pandas hashtable PyObjectHashTable get item  pandas hashtable c 12322     KeyError   predictedY   During handling of the above exception  another exception occurred   KeyError                                  Traceback  most recent call last  C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas core internals py in set self  item  value  check     3414         try  - gt  3415             loc   self items get loc item     3416         except KeyError   C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas indexes base py in get loc self  key  method  tolerance     1946             except KeyError  - gt  1947                 return self  engine get loc self  maybe cast indexer key      1948   pandas index pyx in pandas index IndexEngine get loc  pandas index c 4154     pandas index pyx in pandas index IndexEngine get loc  pandas index c 4018     pandas hashtable pyx in pandas hashtable PyObjectHashTable get item  pandas hashtable c 12368     pandas hashtable pyx in pandas hashtable PyObjectHashTable get item  pandas hashtable c 12322     KeyError   predictedY   During handling of the above exception  another exception occurred   ValueError                                Traceback  most recent call last   lt ipython-input-95-476dc59cd7fa gt  in  lt module gt         26     return gp  results      27  --- gt  28 gp dailyElectricity  results dailyElectricity   predictAll 3  0 04  trainX dailyElectricity  trainY dailyElectricity  testX dailyElectricity  testY dailyElectricity  testSet dailyElectricity   Daily Electricity     lt ipython-input-95-476dc59cd7fa gt  in predictAll theta  nugget  trainX  trainY  testX  testY  testSet  title        8        9     results   testSet copy   --- gt  10     results  predictedY     predictedY      11     results  sigma     sigma      12   C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas core frame py in   setitem   self  key  value     2355         else     2356               set column - gt  2357             self  set item key  value     2358     2359     def  setitem slice self  key  value    C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas core frame py in  set item self  key  value     2422         self  ensure valid index value     2423         value   self  sanitize column key  value  - gt  2424         NDFrame  set item self  key  value     2425     2426           check if we are modifying a copy  C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas core generic py in  set item self  key  value     1462     1463     def  set item self  key  value   - gt  1464         self  data set key  value     1465         self  clear item cache      1466   C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas core internals py in set self  item  value  check     3416         except KeyError     3417               This item wasn t present  just insert at end - gt  3418             self insert len self items   item  value     3419             return    3420   C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas core internals py in insert self  loc  item  value  allow duplicates     3517     3518         block   make block values value  ndim self ndim  - gt  3519                            placement slice loc  loc   1      3520     3521         for blkno  count in  fast count smallints self  blknos loc      C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas core internals py in make block values  placement  klass  ndim  dtype  fastpath     2516                      placement placement  dtype dtype     2517  - gt  2518     return klass values  ndim ndim  fastpath fastpath  placement placement     2519     2520   TODO  flexible with index None and or items None  C  Users brennn1 AppData Local Continuum Anaconda3 lib site-packages pandas core internals py in   init   self  values  placement  ndim  fastpath       88             raise ValueError  Wrong number of items passed  d  placement        89                               implies  d     len self values   --- gt  90                                              len self mgr locs         91       92      property  ValueError  Wrong number of items passed 3  placement implies 1   My code is as follows   def predictAll theta  nugget  trainX  trainY  testX  testY  testSet  title        gp   gaussian process GaussianProcess theta0 theta  nugget  nugget      gp fit trainX  trainY       predictedY  MSE   gp predict testX  eval MSE   True      sigma   np sqrt MSE       results   testSet copy       results  predictedY     predictedY     results  sigma     sigma      print   Train score R2    gp score trainX  trainY       print   Test score R2    sklearn metrics r2 score testY  predictedY        plt figure figsize    9 8       plt scatter testY  predictedY      plt plot  min testY   max testY     min testY   max testY     r       plt xlim  min testY   max testY        plt ylim  min testY   max testY        plt title  Predicted vs  observed      title      plt xlabel  Observed       plt ylabel  Predicted       plt show        return gp  results  gp dailyElectricity  results dailyElectricity   predictAll 3  0 04  trainX dailyElectricity  trainY dailyElectricity  testX dailyElectricity  testY dailyElectricity  testSet dailyElectricity   Daily Electricity

User · Answer

Not sure if this is relevant to your question but it might be relevant to someone else in the future  I had a similar error  Turned out that the df was empty  had zero rows  and that is what was causing the error in my command

User · Answer

for i in range 100   try     Your code here   break except    continue  This one worked for me

User · Answer

In general  the error ValueError  Wrong number of items passed 3  placement implies 1 suggests that you are attempting to put too many pigeons in too few pigeonholes  In this case  the value on the right of the equation  results  predictedY     predictedY   is trying to put 3  things  into a container that allows only one  Because the left side is a dataframe column  and can accept multiple items on that  column  dimension  you should see that there are too many items on another dimension    Here  it appears you are using sklearn for modeling  which is where gaussian process GaussianProcess   is coming from  I m guessing  but correct me and revise the question if this is wrong     Now  you generate predicted values for y here    predictedY  MSE   gp predict testX  eval MSE   True   However  as we can see from the documentation for GaussianProcess  predict   returns two items  The first is y  which is array-like  emphasis mine   That means that it can have more than one dimension  or  to be concrete for thick headed people like me  it can have more than one column -- see that it can return  n samples  n targets  which  depending on testX  could be  1000  3   just to pick numbers   Thus  your predictedY might have 3 columns    If so  when you try to put something with three  columns  into a single dataframe column  you are passing 3 items where only 1 would fit

[python] ValueError: Wrong number of items passed - Meaning and suggestions?

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