Pandas: Difference between largest and smallest value within group

Question

Given a data frame that looks like this

GROUP VALUE
  1     5
  2     2
  1     10
  2     20
  1     7

I would like to compute the differe

Answer 1

You can use groupby(), min(), and max():

df.groupby('GROUP')['VALUE'].apply(lambda g: g.max() - g.min())