Adding new column to existing DataFrame in Python pandas

Question

I have the following indexed DataFrame with named columns and rows not- continuous numbers:

          a         b         c         d
2  0.671399  0.101208 -         


        

Answer 1

I was looking for a general way of adding a column of numpy.nans to a dataframe without getting the dumb SettingWithCopyWarning.

From the following:

• the answers here
• this question about passing a variable as a keyword argument
• this method for generating a numpy array of NaNs in-line

I came up with this:

col = 'column_name'
df = df.assign(**{col:numpy.full(len(df), numpy.nan)})