Python beginner : raise ValueError('Must have equal len keys and value ')

Question

I would like to fill in an existing dataframe another column. The column will contain the value of a dictionary. And those values are list of tokens. So far, it is not working, is there a way to add them to the dataframe?

df = pd.read_csv(sys.argv[1], na_values=['no info', '.'], encoding='Cp1252', delimiter=';')
s = pd.DataFrame(dict1).T.reset_index()
print(s)
#result

''' 
     index      0      1     2
0      231   2470  11854  2368
1      236   3132  11130  1236
2      237   4527  14593  1924
3      238   6167   8222  1070
'''
s.columns = ['number','grade1','grade2','grade3']
print(s.head())

#result
''' 
     number  grade1 grade2 grade3     
0      231   2470  11854  2368
1      236   3132  11130  1236
2      237   4527  14593  1924
3      238   6167   8222  1070
'''

df=pd.concat([df,s],axis=1)
print(df)
#result
'''
        id  ...        grade3
0      231  ...        2368
1      236  ...        1236
'''
#Filling to excel file
df.to_excel('exit_test2.xlsx')

#filling a new column with a list of tokens for each cell. The key of two dict are the same so I just need the list of tokens

df['tokens'] = ' '
for k,v in dict2.items():
    df.at[int(k), 'tokens'] = v 
print(df)
#have error 

traceback error

  File "Script_JDM_sans_sens.py", line 101, in <module>
    df.at[int(k), 'tokens'] = v  #change -1 for verbatim
  File "C:\Anaconda3\lib\site-packages\pandas\core\indexing.py", line 2287, in __setitem__
    self.obj._set_value(*key, takeable=self._takeable)
  File "C:\Anaconda3\lib\site-packages\pandas\core\frame.py", line 2823, in _set_value
    self.loc[index, col] = value
  File "C:\Anaconda3\lib\site-packages\pandas\core\indexing.py", line 190, in __setitem__
    self._setitem_with_indexer(indexer, value)
  File "C:\Anaconda3\lib\site-packages\pandas\core\indexing.py", line 611, in _setitem_with_indexer
    raise ValueError('Must have equal len keys and value '
ValueError: Must have equal len keys and value when setting with an iterable

#Display of dict2

dict2 = {'231': ['look','eat','at'], '236': ['lay','good', 'fun'], ….}

How can I resolve this error?

Answer 1

You can convert dict2 to a pandas' Series object and then add that series as a column of you DataFrame df.

Convert dict2 to Series:

s = pd.Series(dict2)

If the 'id' column in df is of type int , you'll have to convert the series index to int :

s.index = s.index.astype(int)

Then, set the index of df to be the same as the Series' index:

df.set_index('id', inplace=True)

And finally add the 'token' column:

df['token'] = s

Here is the result:

        grade1  grade2  grade3  token
id              
231     2470    11854   2368    [look, eat, at]
236     3132    11130   1236    [lay, good, fun]
237     4527    14593   1924    NaN
238     6167    8222    1070    NaN

Answer 2

You need to set index of df to column id . It currently is rangeindex . Try this

df['tokens'] = ' '
df = df.set_index('id')
for k,v in dict2.items():
    df.at[int(k), 'tokens'] = v