Create a column which increments value for changes in another row

Question

I have a dataframe with two columns as below:

Var1Var2
a   28
b   28
d   28
f   29
f   29
e   30
b   30
m   30
l   30
u   31
t   31
t   31

I\'d

Answer 1

Something like this:

(df.Var2.diff() != 0).cumsum()