How to Fix: “ValueError: if using all scalar values, you must pass an index”

In this article, we will discuss what is “ValueError: if using all scalar values, you must pass an index”? how you can solve this, and briefly explained examples of it. Now, lets proceed with : …

“ValueError if using all scalar values, you must pass an index”

In this article, we will discuss what is “ValueError: if using all scalar values, you must pass an index”? how you can solve this, and briefly explained examples of it.

Now, lets proceed with :

What is ValueError: if using all scalar values, you must pass an index.

this exception is divided into two parts:

ValueError and if using all scalar values, you must pass an index.

And these two parts stands for:

ValueError: means the error is arising due to some improper value passed as an argument.

If using all scalar values, you must pass an index means while creating an dictionary or list if you are using all the scalar values then you should must pass an index.

How could you solve this exception?

You can solve this:

  • By placing scalar values into dictionary.
  • Transform the scalar values into list.
  • Pass scalar values and pass index.

Let’s understand these methods better with the help of examples.

Example1:
import pandas as pds
dict_student = {
'paul':'38',
'timmy':'50',
'amber':'49',
'rida' :'77'
}
data_frame = pds.DataFrame.from_dict(dict_student)
print(data_frame)

Output:

ValueError                                Traceback (most recent call last)
<ipython-input-5-4903f0f160a7> in <module>
      8 }
      9 
---> 10 data_frame = pds.DataFrame.from_dict(dict_student)
     11 print(data_frame)
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/frame.py in from_dict(cls, data, orient, dtype, columns)
   1307             raise ValueError("only recognize index or columns for orient")
   1308 
-> 1309         return cls(data, index=index, columns=columns, dtype=dtype)
   1310 
   1311     def to_numpy(
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/frame.py in __init__(self, data, index, columns, dtype, copy)
    466 
    467         elif isinstance(data, dict):
--> 468             mgr = init_dict(data, index, columns, dtype=dtype)
    469         elif isinstance(data, ma.MaskedArray):
    470             import numpy.ma.mrecords as mrecords
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/internals/construction.py in init_dict(data, index, columns, dtype)
    281             arr if not is_datetime64tz_dtype(arr) else arr.copy() for arr in arrays
    282         ]
--> 283     return arrays_to_mgr(arrays, data_names, index, columns, dtype=dtype)
    284 
    285 
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/internals/construction.py in arrays_to_mgr(arrays, arr_names, index, columns, dtype, verify_integrity)
     76         # figure out the index, if necessary
     77         if index is None:
---> 78             index = extract_index(arrays)
     79         else:
     80             index = ensure_index(index)
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/internals/construction.py in extract_index(data)
    385 
    386         if not indexes and not raw_lengths:
--> 387             raise ValueError("If using all scalar values, you must pass an index")
    388 
    389         if have_series:

ValueError: If using all scalar values, you must pass an index

In this above example, as you can see that we passed simple scalar values and pandas expecting the list values or dictionary values in that case with the scalar values we must pass an index, that we have not passed in above code ,that’s why it is showing us error message “ValueError: if using all scalar values, you must pass an index.”

Method1:

By placing scalar values into dictionary.

Corrected Example1:

import pandas as pds

dict_student = {
'paul':['38'],
'timmy':['50'],
'amber':['49'],
'rida' :['77']
}

data_frame = pds.DataFrame.from_dict(dict_student)
print(data_frame)

Output

     paul  timmy amber rida
0    38     50    49   77

in above corrected example1, we just passed the scalar values as dictionary items with index and it is displaying an output.

Let’s take another example:

Example2:

# Import pandas module
import pandas as pds

# convert dictionary to a data frame

data_frame = pds.DataFrame({'Alice':56,'Bina':66})
print(data_frame)

Output:

ValueError                                Traceback (most recent call last)
<ipython-input-3-fa166610be18> in <module>
      3 
      4 # convert dictionary to a data frame
----> 5 data_frame = pds.DataFrame({'Alice':56,'Bina':66})
      6 print(data_frame)
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/frame.py in __init__(self, data, index, columns, dtype, copy)
    466 
    467         elif isinstance(data, dict):
--> 468             mgr = init_dict(data, index, columns, dtype=dtype)
    469         elif isinstance(data, ma.MaskedArray):
    470             import numpy.ma.mrecords as mrecords
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/internals/construction.py in init_dict(data, index, columns, dtype)
    281             arr if not is_datetime64tz_dtype(arr) else arr.copy() for arr in arrays
    282         ]
--> 283     return arrays_to_mgr(arrays, data_names, index, columns, dtype=dtype)
    284 
    285 
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/internals/construction.py in arrays_to_mgr(arrays, arr_names, index, columns, dtype, verify_integrity)
     76         # figure out the index, if necessary
     77         if index is None:
---> 78             index = extract_index(arrays)
     79         else:
     80             index = ensure_index(index)
/srv/conda/envs/notebook/lib/python3.6/site-packages/pandas/core/internals/construction.py in extract_index(data)
    385 
    386         if not indexes and not raw_lengths:
--> 387             raise ValueError("If using all scalar values, you must pass an index")
    388 
    389         if have_series:

ValueError: If using all scalar values, you must pass an index

 In above example, we directly just converted dictionary into the dataframe, and the values of the dictionary are scalar, we did not added any index in it that’s why it is showing us “ValueError: if using all scalar values, you must pass an index”.

Method2:

Transform the scalar values into list.

Corrected Example2:
import pandas as pds

# convert dictionary to a data frame
data_frame = pds.DataFrame({'Alice':[56],'Bina':[66]})
print(data_frame)

Output:

     Alice  Bina
0     56    66

In this above corrected example2, we just added index to dictionary items by placing the scalar values inside the square[ ] bracket.

Method3:

Pass scalar values and pass index.

We can also write the above corrected example2 in another way as given below:

import pandas as pds

# convert dictionary to a data frame
data_frame = pds.DataFrame({'Alice':56,'Bina':66}, index=[0])
print(data_frame)

 This will also give us the same output. 

Let’s check it out:

Output:
   Alice  Bina
0     56    66

Conclusion:

“ValueError: if using all scalar values, you must pass an index” in this article we disused three different methods that you can use to solve this error.

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