CODEWITHSUNDEEP
pythonpandasdata-science
Kiran
Kiran

Reputation: 2427

How to resolve Assertion Error for multiple columns in pandas

Pandas documentation has given following code, which works fine:

 frame = pd.DataFrame(np.arange(12).reshape((4, 3)),
     index=[['a', 'a', 'b', 'b'], [1, 2, 1, 2]],
     columns=[['Ohio', 'Ohio', 'Colorado'],
     ['Green', 'Red', 'Green']])

I tried following code, based on above concept, but it does not work:

hi5 = pd.DataFrame([[1,2,3],[4,5,6],[7,8,9],[10,11,12]], 
    index = [['a','a','a','b'],[1,2,3,1]], 
    columns=[['Ohio', 'Ohio', 'Colorado'], 
    ['Green', 'Red', 'Green']])

It is giving Following error for above code:

AssertionError: 2 columns passed, passed data had 3 columns

Upvotes: 1

Views: 1844

Answers (2)

KWx
KWx

Reputation: 310

I think it goes deeper:

The code below works:

frame = pd.DataFrame(np.array([[ 0,  1,  2], [ 3,  4,  5], [ 6,  7,  8], [ 9, 10, 11]]),
index=[['a', 'a', 'a', 'b'], [1, 2, 3, 1]],
columns=[['Ohio', 'Ohio', 'Colorado'],
['Green', 'Red', 'Green']])

The code below doesn't work, the only difference is we're now passing a list instead of an array:

frame = pd.DataFrame([[ 0,  1,  2], [ 3,  4,  5], [ 6,  7,  8], [ 9, 10, 11]],
index=[['a', 'a', 'a', 'b'], [1, 2, 3, 1]],
columns=[['Ohio', 'Ohio', 'Colorado'],
['Green', 'Red', 'Green']])

AssertionError: 2 columns passed, passed data had 3 columns

However, if we split this code up into steps, it works again.

frame = pd.DataFrame([[ 0,  1,  2], [ 3,  4,  5], [ 6,  7,  8], [ 9, 10, 11]])
frame.index=[['a', 'a', 'a', 'b'], [1, 2, 3, 1]]
frame.columns=[['Ohio', 'Ohio', 'Colorado'],
['Green', 'Red', 'Green']]

Upvotes: 1

crayxt
crayxt

Reputation: 2405

Apparently, you will need to use a pd.DataFrame.from_records constructor for that

>>> hi5 = pd.DataFrame.from_records([[1,2,3],[4,5,6],[7,8,9],[10,11,12]],
...     index = [['a','a','a','b'],[1,2,3,1]],
...     columns=[['Ohio', 'Ohio', 'Colorado'],
...     ['Green', 'Red', 'Green']])
>>>
>>> hi5
     Ohio     Colorado
    Green Red    Green
a 1     1   2        3
  2     4   5        6
  3     7   8        9
b 1    10  11       12

I can only guess that list of lists does not have a shape property, thus generic constructor does not support such type of data.

Upvotes: 1

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