Counting Words in a Column in a DataFrame

I have a DataFrames like shown below:

DF1 =

 sID   token     A  B  C  D
  10    I am     a  f  g  h
  10    here     a  g  g  h
  10    whats    a  h  g  h
  10    going    a  o  g  h
  10    on       a  j  g  h
  10    .        a  f  g  h
  11    I am     a  f  g  h
  11    foo bar  a  f  g  h
  12    You are  a  f  g  h
  ...

Is there a way to add a counter column which counts the words (delimited by white space) to the DataFrame. That column should start counting the amount of tokens for each sID

DF2 =

 sID   token     A  B  C  D   Counter
  10    I am     a  f  g  h    0 1
  10    here     a  g  g  h    2
  10    whats    a  h  g  h    3
  10    going    a  o  g  h    4
  10    on       a  j  g  h    5
  10    .        a  f  g  h    6
  11    I am     a  f  g  h    0 1
  11    foo bar  a  f  g  h    2 3
  12    You are  a  f  g  h    0 1
  ...

from Counting Words in a Column in a DataFrame