Typeerror: Cannot Concatenate A Non-ndframe Object

I have this DatetimeIndex: dates = DatetimeIndex(['2017-06-09', '2017-06-10', '2017-06-11', '2017-06-12', '2017-06-13', '2017-06-14'], dtype='datetime6

Solution 1:

If length of df is same as DatetimeIndex and need create index:

df.index = dates 

If not try filter by length of index what is same as length of df:

df.index = dates[:len(df.index)]

If need new column:

df['a'] = dates 

If not:

df['a'] = dates[:len(df.index)]

If need use only first 5 values:

df['a'] = dates[:5]

EDIT:

I think you need union for concatenate index to dates and then reindex:

df=df.reindex(df.index.union(dates),fill_value=-0.944868)print(df)2017-06-05   -0.9448682017-06-06    0.0736232017-06-07   -0.6872322017-06-09   -0.9448682017-06-10   -0.9448682017-06-11   -0.9448682017-06-12   -0.9448682017-06-13   -0.9448682017-06-14   -0.944868Name:<DateOffset>,dtype:float64