Index must be called with a collection of some kind: assign column name to dataframe

Question

I have reweightTarget as follows and I want to convert it to a pandas Dataframe. However, I got following error:

TypeError: Index(...) must be called with a collection of some kind, 't' was passed

If I remove columns='t', it works fine. Can anyone please explain what's going on?

reweightTarget   Trading dates 2004-01-31    4.35 2004-02-29    4.46 2004-03-31    4.44 2004-04-30    4.39 2004-05-31    4.50 2004-06-30    4.53 2004-07-31    4.63 2004-08-31    4.58 dtype: float64 pd.DataFrame(reweightTarget, columns='t')   --------------------------------------------------------------------------- TypeError                                 Traceback (most recent call last) <ipython-input-334-bf438351aaf2> in <module>() ----> 1 pd.DataFrame(reweightTarget, columns='t')  C:\Anaconda3\lib\site-packages\pandas\core\frame.py in __init__(self, data, index, columns, dtype, copy)     253             else:     254                 mgr = self._init_ndarray(data, index, columns, dtype=dtype, --> 255                                          copy=copy)     256         elif isinstance(data, (list, types.GeneratorType)):     257             if isinstance(data, types.GeneratorType):  C:\Anaconda3\lib\site-packages\pandas\core\frame.py in _init_ndarray(self, values, index, columns, dtype, copy)     421                     raise_with_traceback(e)     422  --> 423         index, columns = _get_axes(*values.shape)     424         values = values.T     425   C:\Anaconda3\lib\site-packages\pandas\core\frame.py in _get_axes(N, K, index, columns)     388                 columns = _default_index(K)     389             else: --> 390                 columns = _ensure_index(columns)     391             return index, columns     392   C:\Anaconda3\lib\site-packages\pandas\indexes\base.py in _ensure_index(index_like, copy)    3407             index_like = copy(index_like)    3408  -> 3409     return Index(index_like)    3410     3411   C:\Anaconda3\lib\site-packages\pandas\indexes\base.py in __new__(cls, data, dtype, copy, name, fastpath, tupleize_cols, **kwargs)     266                          **kwargs)     267         elif data is None or lib.isscalar(data): --> 268             cls._scalar_data_error(data)     269         else:     270             if (tupleize_cols and isinstance(data, list) and data and  C:\Anaconda3\lib\site-packages\pandas\indexes\base.py in _scalar_data_error(cls, data)     481         raise TypeError('{0}(...) must be called with a collection of some '     482                         'kind, {1} was passed'.format(cls.__name__, --> 483                                                       repr(data)))     484      485     @classmethod  TypeError: Index(...) must be called with a collection of some kind, 't' was passed 

Answer 1

Documentation: http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.html

columns : Index or array-like

Column labels to use for resulting frame. Will default to np.arange(n) if no column labels are provided

Example:

df3 = DataFrame(np.random.randn(10, 5), columns=['a', 'b', 'c', 'd', 'e'])

Try to use:

pd.DataFrame(reweightTarget, columns=['t']) 

Answer 2

When you want to set an index or columns in data frame you must pass it as a list, so either:

pd.DataFrame(reweightTarget, columns=['t'])  pd.DataFrame(reweightTarget, columns=list('t'))