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

Doing this directly via NumPy will be the most efficient:

df1['e'] = np.random.randn(sLength)

---

Note my original (very old) suggestion was to use map (which is much slower):

df1['e'] = df1['a'].map(lambda x: np.random.random())